title stringlengths 12 150 | question_id int64 469 40.1M | question_score int64 2 5.52k | question_date stringdate 2008-08-02 15:11:16 2016-10-18 06:16:31 | answer_id int64 536 40.1M | answer_score int64 7 8.38k | answer_date stringdate 2008-08-02 18:49:07 2016-10-18 06:19:33 | tags listlengths 1 5 | question_body_md stringlengths 15 30.2k | answer_body_md stringlengths 11 27.8k |
|---|---|---|---|---|---|---|---|---|---|
python using variables from another file | 14,573,021 | 8 | 2013-01-28T23:14:53Z | 14,573,181 | 20 | 2013-01-28T23:30:30Z | [
"python"
] | I'm new and trying to make a simple random sentence generator-
How can I pull a random item out of a list that is stored in another .py document?
I'm using
```
random.choice(verb_list)
```
to pull from the list. How do I tell python that verb\_list is in another document?
Also it would be helpful to know what the pr... | You can import the variables from the file:
**vardata.py**
```
verb_list = [x, y, z]
other_list = [1, ,2, 3]
something_else = False
```
**mainfile.py**
```
from vardata import verb_list, other_list
import random
print random.choice(verb_list)
```
you can also do:
```
from vardata import *
```
to import everythi... |
How do I include related model fields using Django Rest Framework? | 14,573,102 | 74 | 2013-01-28T23:22:19Z | 14,581,826 | 107 | 2013-01-29T11:27:15Z | [
"python",
"django",
"django-rest-framework"
] | Let's say that we have the following model:
```
class Classroom(models.Model):
room_number = [....]
class Teacher(models.Model):
name = [...]
tenure = [...]
classroom = models.ForeignKey(Classroom)
```
Let's say that instead of getting a result like this per the ManyRelatedPrimaryKeyField function:
... | The simplest way is to use [the depth argument](http://django-rest-framework.org/api-guide/serializers#specifiying-nested-serialization)
```
class ClassroomSerializer(serializers.ModelSerializer):
class Meta:
model = Classroom
depth = 1
```
However, that will only include relationships for forward... |
How does using the try statement avoid a race condition? | 14,574,518 | 15 | 2013-01-29T02:05:18Z | 14,574,562 | 7 | 2013-01-29T02:11:20Z | [
"python",
"race-condition"
] | When determining whether or not a file exists, how does using the try statement avoid a "race condition"?
I'm asking because a highly upvoted [answer](http://stackoverflow.com/a/85237/1217270) (update: it was deleted) seems to imply that using `os.path.exists()` creates an opportunity that would not exist otherwise.
... | Here's an example of usage:
```
try:
with open('filename') as f:
do_stuff_that_depends_on_the_existence_of_the_file(f)
except IOError as e:
print 'Trouble opening file'
```
If you are opening the file with any access at all, then the OS will guarantee that the file exists, or else it will fail with an... |
How does using the try statement avoid a race condition? | 14,574,518 | 15 | 2013-01-29T02:05:18Z | 14,575,508 | 18 | 2013-01-29T04:08:56Z | [
"python",
"race-condition"
] | When determining whether or not a file exists, how does using the try statement avoid a "race condition"?
I'm asking because a highly upvoted [answer](http://stackoverflow.com/a/85237/1217270) (update: it was deleted) seems to imply that using `os.path.exists()` creates an opportunity that would not exist otherwise.
... | The race condition is, of course, between your program and some other code that operates on file (race condition always requires at least two parallel processes or threads, see [this](http://en.wikipedia.org/wiki/Race_condition) for details). That means using `open()` instead of `exists()` may really help only in two s... |
Why does this python code have a syntax error? | 14,574,916 | 2 | 2013-01-29T02:56:12Z | 14,574,929 | 7 | 2013-01-29T02:58:21Z | [
"python"
] | To practice python, I made a simple class for a tree structure in which each node can have infinite child nodes.
```
class Tree():
def __init__(self, children, val):
self.children = children
self.val = val
def add(self, child):
self.children.append(child)
def remove(self, index):
child = self.... | In Python 2 `print` is a keyword, so you can't use it as the name of a function or method. |
How to create a list that exceeds the maximum size in Python | 14,576,838 | 6 | 2013-01-29T06:21:35Z | 25,275,253 | 9 | 2014-08-12T22:39:38Z | [
"python",
"list"
] | According to [this](http://stackoverflow.com/questions/855191/how-big-can-a-python-array-get), *The maximum size of a Python list on a 32 bit system is 536,870,912 elements*.
Is there any possible way to initialize a list with bigger size than that?
Let's say:
```
list1 = [None]*1000000000
``` | Lists that large would take up a massive amount of space, as each element in the list would occupy at least 4 bytes, so just one list with maximum allowed elements would take up minimum 2GB of RAM1. And that's without even considering 64-bit systems2.
1. `4 * 5.4e+8 = 2.1e+9`, 2.1 GB
2. `8 * 1.2e+18 = 9.2+18`, 9.2 EB ... |
multiprocessing.Pool spawning new childern after terminate() on Linux/Python2.7? | 14,579,474 | 3 | 2013-01-29T09:24:18Z | 14,583,746 | 11 | 2013-01-29T13:11:33Z | [
"python",
"linux",
"multiprocessing",
"subprocess"
] | I have an executable file which I need to run very often, with different parameters. For this I wrote a small Python (2.7) wrapper, using the multiprocessing module, following the pattern given [here](http://stackoverflow.com/a/2561809/152439.).
My code looks like this:
```
try:
logging.info("starting pool runs"... | On [this page](http://jessenoller.com/2009/01/08/multiprocessingpool-and-keyboardinterrupt/), Jesse Noller, author of the multiprocessing module, shows that the correct way to handle `KeyboardInterrupt` is to have the subprocesses return -- not reraise the exception. This allows the main process to terminate the pool.
... |
How do I concatenate two matrices in Python OpenCV? | 14,579,541 | 6 | 2013-01-29T09:28:09Z | 14,584,537 | 8 | 2013-01-29T13:49:52Z | [
"python",
"opencv"
] | How do I concatenate two matrices into one matrix? The resulting matrix should have the same height as the two input matrices, and its width will equal the sum of the width of the two input matrices.
I am looking for a pre-existing method that will perform the equivalent of this code:
```
def concatenate(mat0, mat1):... | If you are using cv2, (you will get Numpy support then), you can use Numpy function `np.hstack((img1,img2))` to do this.
eg :
```
import cv2
import numpy as np
# Load two images of same size
img1 = cv2.imread('img1.jpg')
img2 = cv2.imread('img2.jpg')
both = np.hstack((img1,img2))
``` |
Getting standard errors on fitted parameters using the optimize.leastsq method in python | 14,581,358 | 14 | 2013-01-29T11:01:04Z | 21,844,726 | 33 | 2014-02-18T04:58:51Z | [
"python",
"scipy",
"data-fitting"
] | I have a set of data (displacement vs time) which I have fitted to a couple of equations using the optimize.leastsq method. I am now looking to get error values on the fitted parameters. Looking through the documentation the matrix outputted is the jacobian matrix, and I must multiply this by the residual matrix to get... | Updated on 4/6/2016
## Getting the correct errors in the fit parameters can be subtle in most cases.
Let's think about fitting a function `y=f(x)` for which you have a set of data points `(x_i, y_i, yerr_i)`, where `i` is an index that runs over each of your data points.
In most physical measurements, the error `yer... |
what does @tornado.web.asynchronous decorator mean? | 14,582,415 | 14 | 2013-01-29T12:02:25Z | 14,605,399 | 15 | 2013-01-30T13:38:52Z | [
"python",
"tornado"
] | 1. If code didn't use this decorator, is it non-blocking?
2. Why this name is asynchronous, it means add decorator let code asynchronous?
3. Why @tornado.gen always use with @tornado.web.asynchronous together? | `@tornado.web.asynchronous` [prevents the the `RequestHandler` from automatically calling `self.finish()`](http://www.tornadoweb.org/en/stable/overview.html#non-blocking-asynchronous-requests). That's it; it just means Tornado will keep the connection open until you manually call `self.finish()`.
1. Code not using thi... |
How to convert output to list to count it amount? | 14,583,339 | 2 | 2013-01-29T12:51:17Z | 14,583,395 | 7 | 2013-01-29T12:54:17Z | [
"python",
"list"
] | I wrote a script that parses a webpage and get the amount of links('a' tag) on it:
```
import urllib
import lxml.html
connection = urllib.urlopen('http://test.com')
dom = lxml.html.fromstring(connection.read())
for link in dom.xpath('//a/@href'):
print link
```
The output of a script:
```
./01.html
./52.html
./... | `link.split()` tries to split link itself. But you must work with entity that represents all links. In your case: `dom.xpath('//a/@href')`.
So this must help you:
```
links = list(dom.xpath('//a/@href'))
```
And getting length with a built-in `len` function:
```
print len(links)
``` |
TypeError: module.__init__() takes at most 2 arguments (3 given) | 14,583,761 | 41 | 2013-01-29T13:12:06Z | 14,584,837 | 84 | 2013-01-29T14:07:33Z | [
"python",
"python-3.x"
] | ```
import Object
class Visitor(Object):
def __init__(self):
super(Visitor,self).__init__()
def visit(self, obj):
pass
def getIsDone(self):
return False
isDone = property(fget =lambda self:self.getIsDone())
```
I get this error: `TypeError: module.__init__() takes at most 2 ar... | ```
class A:pass
print(A) #outputs <class '__main__.A'>
import urllib
print(urllib) #outputs <module 'urllib' from '/usr/lib/python3.2/urllib/__init__.py'>
```
Your error is happening because `Object` is a module, not a class. So your inheritance is screwy.
Change your import statement to:
```
f... |
Django Rest Framework - How to add custom field in ModelSerializer | 14,583,816 | 31 | 2013-01-29T13:15:18Z | 14,584,287 | 32 | 2013-01-29T13:38:57Z | [
"python",
"django",
"django-rest-framework"
] | I created a `ModelSerializer` and want to add a custom field which is not part of my model.
I found a description to add extra fields [here](http://django-rest-framework.org/api-guide/serializers.html#specifying-fields-explicitly) and I tried the following:
```
customField = CharField(source='my_field')
```
When I a... | You're doing the right thing, except that `CharField` (and the other typed fields) are for writable fields.
In this case you just want a simple read-only field, so instead just use:
```
customField = Field(source='get_absolute_url')
``` |
Django Rest Framework - How to add custom field in ModelSerializer | 14,583,816 | 31 | 2013-01-29T13:15:18Z | 21,270,278 | 10 | 2014-01-21T22:21:10Z | [
"python",
"django",
"django-rest-framework"
] | I created a `ModelSerializer` and want to add a custom field which is not part of my model.
I found a description to add extra fields [here](http://django-rest-framework.org/api-guide/serializers.html#specifying-fields-explicitly) and I tried the following:
```
customField = CharField(source='my_field')
```
When I a... | here answer for your question.
you should add to your model Account:
```
@property
def my_field(self):
return None
```
now you can use:
```
customField = CharField(source='my_field')
```
source: <http://stackoverflow.com/a/18396622/3220916> |
Django Rest Framework - How to add custom field in ModelSerializer | 14,583,816 | 31 | 2013-01-29T13:15:18Z | 29,475,731 | 9 | 2015-04-06T16:56:44Z | [
"python",
"django",
"django-rest-framework"
] | I created a `ModelSerializer` and want to add a custom field which is not part of my model.
I found a description to add extra fields [here](http://django-rest-framework.org/api-guide/serializers.html#specifying-fields-explicitly) and I tried the following:
```
customField = CharField(source='my_field')
```
When I a... | ...for clarity, if you have a Model Method defined in the following way:
```
class MyModel(models.Model):
...
def model_method(self):
return "some_calculated_result"
```
You can add the result of calling said method to your serializer like so:
```
class MyModelSerializer(serializers.ModelSerializer)... |
Passing memoryview to C function | 14,584,439 | 13 | 2013-01-29T13:45:47Z | 14,585,530 | 15 | 2013-01-29T14:44:09Z | [
"python",
"numpy",
"cython"
] | I have a C function declared as follows:
```
void getIndexOfState(long *p, long C, long G, long B, long *state);
```
Nowadays my cython wrapper code uses the buffer syntax from numpy array:
```
cpdef int getIndexOfState(self, np.ndarray[np.int_t, ndim=1, mode="c"] s):
cdef long out
getIndexOfState(&out, self... | If the underlying data is [properly contiguous/strided](http://docs.cython.org/src/userguide/memoryviews.html#specifying-more-general-memory-layouts) and there is at least one element in the memory, then it should suffice to pass a pointer to the first element (and maybe the length):
```
getIndexOfState(&out, self.C, ... |
Learning about Queue module in python (how to run it) | 14,585,597 | 3 | 2013-01-29T14:47:21Z | 14,586,659 | 16 | 2013-01-29T15:41:48Z | [
"python",
"multithreading",
"python-3.x",
"queue"
] | Was recently introduced to the queue design in regards to ability to defer processing as well as implementing a "FIFO" etc.
Looked through the documentation in attempt to get a sample queue going to understand how to implement it in my own design / program. But I'm having issues with just running this code:
```
impor... | The for loop is launching a number of worker threads to perform the function defined by "worker". Here is working code that should run on your system in python 2.7.
```
import Queue
import threading
# input queue to be processed by many threads
q_in = Queue.Queue(maxsize=0)
# output queue to be processed by one thre... |
making a class callable in same instance | 14,585,987 | 5 | 2013-01-29T15:07:24Z | 14,586,103 | 8 | 2013-01-29T15:14:01Z | [
"python",
"class",
"callable"
] | ```
class Foo(object):
def tick(self):
print("something")
class Bar(object):
def __init__(self):
self.foo = Foo()
def tick(self):
#Here's what I do....
self.foo.tick()
#here's what my goal would be
self.foo()
b = Bar()
b.tick()
```
That's essentially my g... | Changing `tick(self)` to `__call__(self)` is the correct solution.
This has nothing to do with memory allocation. All `__call__` signifies is the function which Python calls when you use (for an object `foo`) the syntax `foo()`.
For your later question: to check whether something is an object, use `isinstance` or `is... |
Oreo colored text possible in matplotlib? | 14,586,173 | 11 | 2013-01-29T15:18:11Z | 14,676,271 | 7 | 2013-02-03T19:20:44Z | [
"python",
"matplotlib"
] | Is there an easy way to have text (specifically axis-label text) with a white outline color, but black fill color. My axis labels fall over portions of my graph that are in some areas are light and others dark, so some label are obscured.
An easy way to solve this problem would be to set the background color of the ax... | You should be able to pull this off using `PathEffects`, and `ax.(x/y)axis.label` or `ax.get_(x/y)ticklabels()` to get the `txt` objects.
See the examples here:
<http://matplotlib.org/examples/pylab_examples/patheffect_demo.html> |
"ImportError: No module named tkinter" when using Pmw | 14,587,980 | 5 | 2013-01-29T16:52:12Z | 14,588,889 | 24 | 2013-01-29T17:40:12Z | [
"python",
"python-2.7",
"tkinter",
"importerror"
] | Here's my problem: I'm running the code in [this](http://code.activestate.com/recipes/271249-how-to-create-linked-optionmenus-or-other-lists-in/) example. I have Python 2.7 and 3 installed on my RaspberryPi but I have checked and double-checked, and I am running the code in 2.7. I've installed Pmw 2.0.0 under 2.7, not ... | Maybe I can help you on how to remove the error.
here are two thoughts:
1) you use python 2.xx and have installed the python 3 pwm module (Tkinter was renamed to tkinter from Python 2 to 3)
2) you do the following before the import and hope it helps:
```
#import tkinter
#Traceback (most recent call last):
# File "... |
docopt + schema validation | 14,588,098 | 4 | 2013-01-29T16:58:46Z | 14,590,233 | 8 | 2013-01-29T18:59:12Z | [
"python",
"validation",
"parsing",
"schema",
"docopt"
] | Is there a better way of handling this validation:
```
#!/usr/bin/env python
""" command.
Usage:
command start ID
command finish ID FILE
command (-h | --help)
command (-v | --version)
Arguments:
FILE input file
PATH out directory
Options:
-h --help Show this screen.
-v --version Show ve... | I would do the following:
```
#!/usr/bin/env python
"""Command.
Usage:
command start ID
command finish ID FILE
command (-h | --help)
command (-v | --version)
Arguments:
ID
FILE input file
Options:
-h --help Show this screen.
-v --version Show version.
"""
from docopt import docopt
from sch... |
FREAK Descriptor with Opencv Python | 14,588,682 | 9 | 2013-01-29T17:28:05Z | 20,632,100 | 7 | 2013-12-17T10:47:11Z | [
"python",
"opencv",
"feature-detection",
"freak"
] | I was trying to implement the FREAK Descriptor in Python using Opencv. Here is the code i'm using:
```
def surf_freak_detect(image,hessianThreshold):
surfDetector = cv2.SURF(hessianThreshold)
surfDetector=cv2.GridAdaptedFeatureDetector(surfDetector,50)
keypoints = surfDetector.detect(image,None)
freak... | If the keypoints are detected properly but the program crashes when generating the descriptors it is because the **descriptor region** (which surrounds the keypoint) comes out of the image and there is a **memory access to a position that does not exist**.
You have to somehow limit the operating region for freak descr... |
How to get instance given a method of the instance? | 14,588,905 | 6 | 2013-01-29T17:41:05Z | 14,588,947 | 10 | 2013-01-29T17:43:06Z | [
"python",
"class",
"methods",
"instance"
] | ```
class MyClass:
def myMethod(self):
pass
myInstance = MyClass()
methodReference = myInstance.myMethod
```
Now can you get a reference to `myInstance` if you now only have access to `methodReference`? | Try this:
```
methodReference.im_self
```
If you are using Python 3:
```
methodReference.__self__
``` |
Creating multiple objects with foreign key | 14,589,362 | 5 | 2013-01-29T18:07:03Z | 14,593,483 | 7 | 2013-01-29T22:48:19Z | [
"python",
"django",
"factory-boy"
] | I need to create ten sample users (`User`) and each of them must have fifty documents (`Doc`). How to do this in tests.py using factoryboy?
```
#factories.py
from app_name.models import *
import factory
from datetime import datetime, timedelta, time
from django.contrib.auth.models import User
class UserFactory(fact... | ```
users = UserFactory.create_batch(10)
for user in users:
doc = DocFactory.create(user=user)
``` |
How to actually upload a file using Flask WTF FileField | 14,589,393 | 6 | 2013-01-29T18:09:26Z | 14,589,898 | 12 | 2013-01-29T18:39:48Z | [
"python",
"python-2.7",
"flask",
"flask-wtforms"
] | In my forms.py file I have I have
```
class myForm(Form):
fileName = FileField()
```
In my views.py file I have
```
form = myForm()
if form.validate_on_submit():
fileName = secure_filename(form.fileName.file.filename)
```
In my .html file I have
```
{% block content %}
<form ac... | Have you looked at this:
<http://flask.pocoo.org/docs/patterns/fileuploads/#uploading-files>
You have to set a few configs such as UPLOAD\_FOLDER etc. You also have to call the save() function which I don't see in your posted code for views.py.
```
file.save(os.path.join(app.config['UPLOAD_FOLDER'], filename))
``` |
How to actually upload a file using Flask WTF FileField | 14,589,393 | 6 | 2013-01-29T18:09:26Z | 23,939,416 | 7 | 2014-05-29T17:33:13Z | [
"python",
"python-2.7",
"flask",
"flask-wtforms"
] | In my forms.py file I have I have
```
class myForm(Form):
fileName = FileField()
```
In my views.py file I have
```
form = myForm()
if form.validate_on_submit():
fileName = secure_filename(form.fileName.file.filename)
```
In my .html file I have
```
{% block content %}
<form ac... | On form.fileName.file, call '.save'.
```
filename = secure_filename(form.fileName.file.filename)
file_path = os.path.join(app.config['UPLOAD_FOLDER'], filename)
form.fileName.file.save(file_path)
```
Make sure to use secure\_filename() to prevent users from putting in bad file names, such as "../../../../home/usernam... |
Python. Matplotlib inverted image | 14,589,642 | 5 | 2013-01-29T18:23:38Z | 14,590,351 | 12 | 2013-01-29T19:05:57Z | [
"python",
"image",
"matplotlib"
] | I haven't an idea what is wrong here.
```
import matplotlib.pyplot as plt
im = plt.imshow(plt.imread('tas.png'))
plt.show()
```
And the Y axis has inverted.
So I wrote an argument `origin='lower'`.
```
im = plt.imshow(plt.imread('tas.png'), origin='lower')
plt.show()
```
And what I have got.
The Y axis came no... | You are running into an artifact of how images are encoded. For historical reasons, the origin of an image is the top left (just like the indexing on 2D array ... imagine just printing out an array, the first row of your array is the first row of your image, and so on.)
Using `origin=lower` effectively flips your imag... |
Use Python Selenium to get span text | 14,590,341 | 5 | 2013-01-29T19:05:43Z | 14,590,619 | 9 | 2013-01-29T19:23:25Z | [
"python",
"selenium"
] | This should be easy, but I can't get it to work. I'm running a little demo using the Google homepage as a test.
Here's my script:
```
from selenium import webdriver
from selenium.common.exceptions import NoSuchElementException
from selenium.webdriver.common.keys import Keys
import time
browser = webdriver.Chrome()
b... | This should do it:
```
from selenium import webdriver
browser = webdriver.Firefox()
browser.get("http://www.google.com")
for elem in browser.find_elements_by_xpath('.//span[@class = "gbts"]'):
print elem.text
```
---
`text` is a property of the `WebElement` class, thus it is not callable.
```
class WebElement(o... |
Support Vector - / Logistic - regression: do you have benchmark results for the boston housing data? | 14,590,879 | 4 | 2013-01-29T19:40:32Z | 14,592,663 | 8 | 2013-01-29T21:30:38Z | [
"python",
"machine-learning",
"regression",
"scikit-learn"
] | I was going to test my implementation of the sklearn support vector regression package by running it on the boston housing prices dataset that ships with sklearn (sklearn.datasets.load\_boston).
After playing around with it for a while (trying different regularization and tube parameters, randomization of cases and cr... | Change the kernel from `rbf` to `linear` will solve the problem. If you want to use `rbf`, try some different parameters, especially for `gamma`. The default `gamma` (`1/# features`) is too large for your case.
This is the parameter I used for linear... |
How to make a RadioField in Flask? | 14,591,202 | 3 | 2013-01-29T20:01:33Z | 14,591,681 | 14 | 2013-01-29T20:31:14Z | [
"python",
"python-2.7",
"flask",
"flask-wtforms"
] | I have a form with a TextField, FileField, and I want to add a RadioField.
I'd like to have a radio field with two options, where the user can only select one. I'm following the example of the two previous forms that work.
My forms.py looks like this
```
from flask import Flask, request
from werkzeug import ... | In the forms.py the RadioField needs to look like this
```
RadioField('Label', choices=[('value','description'),('value_two','whatever')])
```
Where the options are 'description' and 'whatever' with the submitted values being 'value' an 'value\_two' respectively. |
How can Linux program, e.g. bash or python script, know how it was started: from command line or interactive GUI? | 14,592,390 | 4 | 2013-01-29T21:12:51Z | 14,592,608 | 8 | 2013-01-29T21:27:12Z | [
"python",
"linux",
"bash",
"user-interface",
"command-line-interface"
] | I want to do the following:
If the bash/python script is launched from a terminal, it shall do something such as printing an error message text. If the script is launched from GUI session like double-clicking from a file browser, it shall do something else, e.g. display a GUI message box. | You can check to see whether `stdin` and `stdout` are connected to a terminal or not. When run from a GUI, generally `stdin` is not connected at all, and `stdout` is connected to a log file. When run from a terminal, both `stdin` and `stdout` will be connected to a terminal.
In Python:
```
import os
import sys
if os... |
Unstable results from Python factoring function | 14,592,649 | 3 | 2013-01-29T21:30:00Z | 14,592,819 | 10 | 2013-01-29T21:40:41Z | [
"python",
"factorization"
] | ```
def test_prime(n):
q = True
for p in range(2,n): #Only need to check up to rootn for primes and n/2 for factors
if int(n%p) is 0:
q = False
print(p, 'and', int(n/p), 'are factors of ', n)
if q:
print(n, 'IS a prime number!')
else:
print(n... | You want `n % p == 0`, not `n % p is 0`. `is` tests identity, not equality, and not every 0 **is** the same as every other 0.
```
>>> 659306 % 329653
0
>>> (659306 % 329653) == 0
True
>>> (659306 % 329653) is 0
False
>>> id(0)
136748976
>>> id(659306 % 329653)
3070888160
```
The `id` there basically corresponds to a... |
A good way to get the charset/encoding of an HTTP response in Python | 14,592,762 | 20 | 2013-01-29T21:36:39Z | 14,592,894 | 16 | 2013-01-29T21:45:28Z | [
"python",
"character-encoding",
"httprequest",
"urllib2"
] | Looking for an easy way to get the charset/encoding information of an HTTP response using Python urllib2, or any other Python library.
```
>>> url = 'http://some.url.value'
>>> request = urllib2.Request(url)
>>> conn = urllib2.urlopen(request)
>>> response_encoding = ?
```
I know that it is sometimes present in the '... | To parse http header you could use [`cgi.parse_header()`](http://docs.python.org/2/library/cgi.html#functions):
```
_, params = cgi.parse_header('text/html; charset=utf-8')
print params['charset'] # -> utf-8
```
Or using the response object:
```
response = urllib2.urlopen('http://example.com')
response_encoding = re... |
How to reorder pixels | 14,593,441 | 2 | 2013-01-29T22:45:21Z | 14,594,003 | 8 | 2013-01-29T23:27:42Z | [
"python",
"image-processing"
] | I have searched on Google but I couldn't find anything.
I want to create a Python script that can import an image, change the order of pixels, and save an output image.
I have worked with Python a lot, but only with the built-in libraries. So if I have to use new commands, please describe it as much as you can. | ```
import sys
import random
from PIL import Image
BLOCKLEN = 64 # Adjust and be careful here.
img = Image.open(sys.argv[1])
width, height = img.size
xblock = width / BLOCKLEN
yblock = height / BLOCKLEN
blockmap = [(xb*BLOCKLEN, yb*BLOCKLEN, (xb+1)*BLOCKLEN, (yb+1)*BLOCKLEN)
for xb in xrange(xblock) for yb i... |
selecting edges based on source/target in igraph | 14,594,009 | 7 | 2013-01-29T23:28:19Z | 14,600,513 | 9 | 2013-01-30T09:27:27Z | [
"python",
"igraph"
] | is there an easy way to select/delete edges based on their source and target in igraph?
what I am using is essentially
```
g.es["source"] = [e.source for e in g.es]
g.es["target"] = [e.target for e in g.es]
g.es["tuple"] = [e.tuple for e in g.es]
g.es.select(target=root)
```
but I feel like there shou... | Just use `_source=whatever` and `_target=whatever` as keyword arguments to `select`, e.g.:
```
g.es.select(_source=root)
```
Alternatively, you can use the `incident` method of the graph, which gives you a list of edge IDs instead of a filtered `EdgeSeq` if that is better for your purposes:
```
g.incident(root, mode... |
Python read-only property | 14,594,120 | 26 | 2013-01-29T23:37:12Z | 14,594,174 | 20 | 2013-01-29T23:42:35Z | [
"python",
"properties",
"python-2.7",
"private",
"readonly"
] | **I don't know when attribute should be private and if I should use property.**
I read recently that setters and getters are not pythonic and I should use property decorator.
It's ok.
But what if I have attribute, that mustn't be set from outside of class but can be read (read-only attribute). Should this attribute b... | Generally, Python programs should be written with the assumption that all users are consenting adults, and thus are responsible for using things correctly themselves. However, in the rare instance where it just does not make sense for an attribute to be settable (such as a derived value, or a value read from some stati... |
Python read-only property | 14,594,120 | 26 | 2013-01-29T23:37:12Z | 15,812,738 | 18 | 2013-04-04T13:30:24Z | [
"python",
"properties",
"python-2.7",
"private",
"readonly"
] | **I don't know when attribute should be private and if I should use property.**
I read recently that setters and getters are not pythonic and I should use property decorator.
It's ok.
But what if I have attribute, that mustn't be set from outside of class but can be read (read-only attribute). Should this attribute b... | Just my two cents, [Silas Ray](http://stackoverflow.com/users/683020) is on the right track, however I felt like adding an example. ;-)
Python is a type-unsafe language and thus you'll always have to trust the users of your code to use the code like a reasonable (sensible) person.
Prefixing a property with an undersc... |
Appengine - Upgrading from standard DB to NDB - ReferenceProperties | 14,595,163 | 6 | 2013-01-30T01:24:07Z | 14,595,379 | 11 | 2013-01-30T01:50:13Z | [
"python",
"database",
"google-app-engine",
"datastore"
] | I have an AppEngine application that I am considering upgrading to use the NDB database.
In my application, I have millions of objects that have old-style db references. I would like to know what the best migration path would be to get these ReferenceProperty values converted to KeyProperty values, or any other soluti... | Good news, you don't have to make any changes to your persisted data, as `ext.db` and `ndb` read and write the exact same data.
Here's the quote from the [NDB Cheat Sheet](https://cloud.google.com/appengine/docs/python/ndb/db_to_ndb):
> ### No Datastore Changes Needed!
>
> In case you wondered, despite the different ... |
AttributeError: 'module' object has no attribute 'ZipFile' | 14,595,280 | 4 | 2013-01-30T01:38:49Z | 14,595,304 | 8 | 2013-01-30T01:41:45Z | [
"python"
] | just like i said,it's a very strange question.i hope you guys could help me solve this question thanks
**the following is my code:**
```
import os
import zipfile
filename = "E:\\test.zip"
currdir = "E:\\vpn\\"
os.chdir(currdir)
tfile = zipfile.ZipFile(filename, 'w')
files = os.listdir(currdir)
for f in files:
... | You called your script `zipfile.py`, which means it is trying to import itself. Change the name of the file to basically anything else. |
Python dateutil.parser throws "ValueError: day is out of range for month" | 14,595,401 | 7 | 2013-01-30T01:52:09Z | 14,595,427 | 10 | 2013-01-30T01:56:06Z | [
"python",
"python-dateutil"
] | I have a the following code that runs fine with input format like `{Year}/{Month}` except when it comes to `1994/02`
Here is the sample code
```
>>> import dateutil.parser as dtp
>>> dtp.parse('1994/01')
datetime.datetime(1994, 1, 29, 0, 0)
>>> dtp.parse('1994/03')
datetime.datetime(1994, 3, 29, 0, 0)
>>> dtp.parse('... | `dtp.parse` is filling in the missing day with the current date's day. You ran the code on 2013/01/29 and day 29 does not exist in February (i.e. 1994/02/29).
Use this instead:
```
dtp.parse('1994/01'+'/01')
```
It will give consistent results (first day of month) regardless of when the code is executed. |
Using Python to convert integer to binary | 14,596,367 | 3 | 2013-01-30T03:49:50Z | 14,596,397 | 10 | 2013-01-30T03:52:43Z | [
"python",
"binary",
"integer"
] | I'm trying to convert integer to binary. This is my work.
I don't know how the make a list to show the binary.
```
num_str = input("Please give me a integer: ")
num_int = int(num_str)
while num_int > 0:
if num_int % 2 == 0:
num_int = int(num_int / 2)
num_remainder = 1
print("The remainde... | Are you aware of the builtin `bin` function?
```
>>> bin(100)
'0b1100100'
>>> bin(1)
'0b1'
>>> bin(0)
'0b0'
``` |
Remove text between () and [] in python | 14,596,884 | 4 | 2013-01-30T04:46:35Z | 14,598,135 | 8 | 2013-01-30T06:42:22Z | [
"python",
"python-2.7"
] | I have a very long string of text with `()` and `[]` in it. I'm trying to remove the characters between the parentheses and brackets but I cannot figure out how.
The list is similar to this:
```
x = "This is a sentence. (once a day) [twice a day]"
```
This list isn't what I'm working with but is very similar and a l... | Run this script, it works even with nested brackets.
Uses basic logical tests.
```
def a(test_str):
ret = ''
skip1c = 0
skip2c = 0
for i in test_str:
if i == '[':
skip1c += 1
elif i == '(':
skip2c += 1
elif i == ']' and skip1c > 0:
skip1c -=... |
Remove text between () and [] in python | 14,596,884 | 4 | 2013-01-30T04:46:35Z | 14,599,280 | 7 | 2013-01-30T08:10:16Z | [
"python",
"python-2.7"
] | I have a very long string of text with `()` and `[]` in it. I'm trying to remove the characters between the parentheses and brackets but I cannot figure out how.
The list is similar to this:
```
x = "This is a sentence. (once a day) [twice a day]"
```
This list isn't what I'm working with but is very similar and a l... | You can use re.sub function.
```
>>> import re
>>> x = "This is a sentence. (once a day) [twice a day]"
>>> re.sub("([\(\[]).*?([\)\]])", "\g<1>\g<2>", x)
'This is a sentence. () []'
```
If you want to remove the [] and the () you can use this code:
```
>>> import re
>>> x = "This is a sentence. (once a day) [twic... |
Custom tab completion in python argparse | 14,597,466 | 19 | 2013-01-30T05:43:49Z | 15,289,025 | 31 | 2013-03-08T07:41:05Z | [
"python",
"bash",
"command-line-interface",
"argparse",
"tab-completion"
] | Is it possible to get smarter tab completion cooperating with `argparse` in python scripts? My shell is bash. The information I can find about this stuff online is over a year old and mostly relates to `optparse`, which I don't want to use (deprecated).
For the following script:
```
#!/usr/bin/env python
import argp... | Have a look at [argcomplete](https://argcomplete.readthedocs.org/en/latest/#activating-global-completion%20argcomplete) by Andrey Kislyuk.
Install it with:
```
sudo pip install argcomplete
```
Import the module and add one line in your source before calling `parser.parse_args()`:
```
#!/usr/bin/env python
import a... |
How to compare 2 list/array with python using for loops? | 14,599,307 | 2 | 2013-01-30T08:11:26Z | 14,599,346 | 7 | 2013-01-30T08:13:52Z | [
"python",
"arrays",
"list"
] | I want to compare ListA[0] to ListB[0]...etc.
```
ListA = [itemA, itemB, itemC]
ListB = [true, false, true]
for item in ListA:
if ListB[item] == True:
print"I have this item"
```
Current problem is that [item] is not a number, so ListB[item] will not work. What is the correct way if I want to do somethin... | You can iterate through the **lists** this way.
```
for a, b in zip(ListA, ListB):
pass
``` |
How to compare 2 list/array with python using for loops? | 14,599,307 | 2 | 2013-01-30T08:11:26Z | 14,599,390 | 8 | 2013-01-30T08:16:15Z | [
"python",
"arrays",
"list"
] | I want to compare ListA[0] to ListB[0]...etc.
```
ListA = [itemA, itemB, itemC]
ListB = [true, false, true]
for item in ListA:
if ListB[item] == True:
print"I have this item"
```
Current problem is that [item] is not a number, so ListB[item] will not work. What is the correct way if I want to do somethin... | You can use `itertools.compress`:
```
Docstring:
compress(data, selectors) --> iterator over selected data
Return data elements corresponding to true selector elements.
Forms a shorter iterator from selected data elements using the
selectors to choose the data elements.
```
---
```
In [1]: from itertools import com... |
Using NOT EXISTS clause in sqlalchemy ORM query | 14,600,619 | 7 | 2013-01-30T09:33:23Z | 14,616,390 | 11 | 2013-01-31T00:21:48Z | [
"python",
"sqlalchemy"
] | I want to convert the following raw sql query into a sqlalchemy ORM query :
```
SELECT * FROM kwviolations AS kwviol WHERE kwviol.proj_id=1 AND NOT EXISTS (SELECT * FROM
kwmethodmetrics AS kwmetrics WHERE kwmetrics.kw_id=kwviol.kw_id AND kwmetrics.checkpoint_id=5);
```
I tried the following ORM query but didn't succe... | `kw_id` here seems to be a scalar column value, so you can't call `any()` on that - `any()` is only available from a [relationship()](http://docs.sqlalchemy.org/en/rel_0_8/orm/relationships.html#sqlalchemy.orm.relationship) bound attribute. Since I don't see one of those here you can call the [exists()](http://docs.sql... |
Why do some Unix commands not work when called from inside Python? (command not found) | 14,601,203 | 3 | 2013-01-30T10:02:48Z | 14,601,615 | 8 | 2013-01-30T10:21:51Z | [
"python",
"shell",
"unix",
"command"
] | I often wish to perform Unix commands from inside Python, but I have found recently that some commands are not found. An example is the 'limit' command:
```
$ echo $SHELL
/bin/tcsh
$ limit vmemoryuse 1000m
$ python
Python 2.7.3 (default, Aug 3 2012, 20:09:51)
[GCC 4.1.2 20080704 (Red Hat 4.1.2-50)] on linux2
Type "h... | That's because some shell commands are not really programs, but internal shell commands.
The classical example is `cd`: if it were an external program it would change the current directory of the new process, not the one of the shell, so it cannot be an external program.
Roughly speaking there are two types of intern... |
Joining 2 list of different size in Python | 14,602,485 | 2 | 2013-01-30T11:05:40Z | 14,602,567 | 8 | 2013-01-30T11:09:41Z | [
"python"
] | I get "list of index out of range" error when try to use 2 different size list.
example:
```
ListA = [None, None, None, None, None]
ListB = ['A', None, 'B']
for x, y in enumerate(ListA):
if ListB[x]:
ListA[x]=ListB[x]
```
Doing this will get "list of index out of range" error, because ListB[3] and ListB... | Use [itertools.izip\_longest](http://docs.python.org/2/library/itertools.html#itertools.izip_longest)
```
from itertools import izip_longest
ListA = [b or a for a, b in izip_longest(ListA,ListB)]
``` |
Creating of new columns in pandas.DataFrame using apply() function | 14,602,739 | 3 | 2013-01-30T11:19:21Z | 14,603,893 | 8 | 2013-01-30T12:21:44Z | [
"python",
"pandas"
] | I have a pandas DataFrame like:
```
A B
'2010-01-01' 10 20
'2010-02-01' 20 30
'2010-03-01' 30 10
```
I need to apply some function for every columns and create new columns in this DataFrame with special name.
```
A B A1 B1
'2010-01-01' 10 20 20 40
'2010-02-01' 20 30... | You can use `join` to do the combining:
```
>>> import pandas as pd
>>> df = pd.DataFrame({"A": [10,20,30], "B": [20, 30, 10]})
>>> df
A B
0 10 20
1 20 30
2 30 10
>>> df * 2
A B
0 20 40
1 40 60
2 60 20
>>> df.join(df*2, rsuffix='1')
A B A1 B1
0 10 20 20 40
1 20 30 40 60
2 30 1... |
Running a standalone script doing a model query in Django with `settings/dev.py` instead of `settings.py` | 14,603,458 | 4 | 2013-01-30T11:59:00Z | 14,603,619 | 7 | 2013-01-30T12:06:38Z | [
"python",
"django",
"django-settings"
] | Note the `settings/dev.py` instead of one `settings.py` file and the `script.py` in `my_app` in the following Django(1.4.3) project:
```
.
âââ my_project
â âââ my_app
â â âââ __init__.py
â â âââ models.py
â â âââ tests.py
â â âââ views.py
â â... | If you're looking to just run a script in the django environment, then the simplest way to accomplish this is to create a `./manage.py` subcommand, like this
```
from django.core.management.base import BaseCommand
from my_app.models import MyModel
class Command(BaseCommand):
help = 'runs your code in the django e... |
How to activate virtualenv? | 14,604,699 | 58 | 2013-01-30T13:02:35Z | 14,604,791 | 8 | 2013-01-30T13:07:38Z | [
"python",
"virtualenv"
] | Newbie here so please be gentle.
I have been through search and tried various alternatives without success and spent several days on it now - driving me mad.
Running on Red Hat Linux with Python 2.5.2
Began using most recent Virtualenv but could not activate it, I found somewhere suggesting needed earlier version so I... | The problem there is the `/bin/.` command. That's really weird, since . should always be a link to the directory it's in. (Honestly, unless `.` is a strange alias or function, I don't even see how it's possible.) It's also a little unusual that your shell doesn't have a `.` [builtin for `source`](http://pubs.opengroup.... |
How to activate virtualenv? | 14,604,699 | 58 | 2013-01-30T13:02:35Z | 14,606,360 | 101 | 2013-01-30T14:27:57Z | [
"python",
"virtualenv"
] | Newbie here so please be gentle.
I have been through search and tried various alternatives without success and spent several days on it now - driving me mad.
Running on Red Hat Linux with Python 2.5.2
Began using most recent Virtualenv but could not activate it, I found somewhere suggesting needed earlier version so I... | Here is my work flow after creating a folder and `cd`'ing into it:
```
$ virtualenv venv --distribute
New python executable in venv/bin/python
Installing distribute.........done.
Installing pip................done.
$ source venv/bin/activate
(venv)$ python
``` |
How to activate virtualenv? | 14,604,699 | 58 | 2013-01-30T13:02:35Z | 24,720,790 | 35 | 2014-07-13T08:20:01Z | [
"python",
"virtualenv"
] | Newbie here so please be gentle.
I have been through search and tried various alternatives without success and spent several days on it now - driving me mad.
Running on Red Hat Linux with Python 2.5.2
Began using most recent Virtualenv but could not activate it, I found somewhere suggesting needed earlier version so I... | You forgot to do `source bin/activate` where source is a executable name.
Struck me first few times as well, easy to think that manual is telling "execute this from root of the environment folder".
PS. no need to make activate executable via chmod, just FYI. |
How to activate virtualenv? | 14,604,699 | 58 | 2013-01-30T13:02:35Z | 34,479,727 | 17 | 2015-12-27T10:57:00Z | [
"python",
"virtualenv"
] | Newbie here so please be gentle.
I have been through search and tried various alternatives without success and spent several days on it now - driving me mad.
Running on Red Hat Linux with Python 2.5.2
Began using most recent Virtualenv but could not activate it, I found somewhere suggesting needed earlier version so I... | You can do
```
source ./python_env/bin/activate
```
or just go to the directory
```
cd /python_env/bin/
```
and then
```
source ./activate
```
Good Luck. |
All permutations of a Windows license key | 14,606,351 | 96 | 2013-01-30T14:27:26Z | 14,606,435 | 58 | 2013-01-30T14:31:24Z | [
"python",
"itertools"
] | I need to apply for a Windows 8 upgrade for my laptop, for which I need the Windows 7 license key on the underside of the laptop.
Because Microsoft decided in their infinite wisdom to create license labels that wear off, and I cannot read my license key clearly, it means I can't register my laptop for the windows upgr... | ```
from itertools import product
for perm in product('8B', 'B8', 'HN', '6G'):
print 'MPP6R-09RXG-2H%sMT-%sK%sM9-V%sC8R' % perm
``` |
All permutations of a Windows license key | 14,606,351 | 96 | 2013-01-30T14:27:26Z | 14,606,540 | 163 | 2013-01-30T14:36:42Z | [
"python",
"itertools"
] | I need to apply for a Windows 8 upgrade for my laptop, for which I need the Windows 7 license key on the underside of the laptop.
Because Microsoft decided in their infinite wisdom to create license labels that wear off, and I cannot read my license key clearly, it means I can't register my laptop for the windows upgr... | **Disclaimer:** Yes, I know that this is not [Python](http://en.wikipedia.org/wiki/Python_%28programming_language%29) code. It just popped into my mind and I simply *had* to write it down.
The simplest way is the use of shell expansion:
```
$ echo MPP6R-09RXG-2H{8,B}MT-{B,8}K{H,N}M9-V{6,G}C8R
MPP6R-09RXG-2H8MT-BKHM9-... |
All permutations of a Windows license key | 14,606,351 | 96 | 2013-01-30T14:27:26Z | 14,606,754 | 9 | 2013-01-30T14:49:11Z | [
"python",
"itertools"
] | I need to apply for a Windows 8 upgrade for my laptop, for which I need the Windows 7 license key on the underside of the laptop.
Because Microsoft decided in their infinite wisdom to create license labels that wear off, and I cannot read my license key clearly, it means I can't register my laptop for the windows upgr... | How about using itertools and functools at the same time?
```
>>> from operator import mod
>>> from functools import partial
>>> from itertools import product
>>> map(partial(mod, 'MPP6R-09RXG-2H%sMT-%sK%sM9-V%sC8R'), product('8B', 'B8', 'HN', '6G'))
['MPP6R-09RXG-2H8MT-BKHM9-V6C8R', 'MPP6R-09RXG-2H8MT-BKHM9-VGC8R', '... |
All permutations of a Windows license key | 14,606,351 | 96 | 2013-01-30T14:27:26Z | 14,612,768 | 16 | 2013-01-30T20:11:08Z | [
"python",
"itertools"
] | I need to apply for a Windows 8 upgrade for my laptop, for which I need the Windows 7 license key on the underside of the laptop.
Because Microsoft decided in their infinite wisdom to create license labels that wear off, and I cannot read my license key clearly, it means I can't register my laptop for the windows upgr... | Another way to generate the combinations
```
>>> ['MPP6R-09RXG-2H%sMT-%sK%sM9-V%sC8R' % (a, b, c, d)
... for a in '8B' for b in 'B8' for c in 'HN' for d in '6G']
['MPP6R-09RXG-2H8MT-BKHM9-V6C8R',
'MPP6R-09RXG-2H8MT-BKHM9-VGC8R',
'MPP6R-09RXG-2H8MT-BKNM9-V6C8R',
'MPP6R-09RXG-2H8MT-BKNM9-VGC8R',
'MPP6R-09RXG-2H8MT-... |
python nested classes | 14,606,559 | 13 | 2013-01-30T14:37:47Z | 14,606,571 | 8 | 2013-01-30T14:39:01Z | [
"python",
"python-3.x"
] | First of all, here's my test code, I'm using python 3.2.x:
```
class account:
def __init__(self):
pass
class bank:
def __init__(self):
self.balance = 100000
def balance(self):
self.balance
def whitdraw(self, amount):
self.balance -= amount
... | There are several problems:
1. You're using the name `balance` for both the data member and for the function.
2. You're missing a `return` statement in `balance()`.
3. `balance()` operates on an *instance* of `bank`. There is no instance in `a.bank.balance`: here, `a.bank` refers to the inner class itself. |
python nested classes | 14,606,559 | 13 | 2013-01-30T14:37:47Z | 14,607,121 | 22 | 2013-01-30T15:06:48Z | [
"python",
"python-3.x"
] | First of all, here's my test code, I'm using python 3.2.x:
```
class account:
def __init__(self):
pass
class bank:
def __init__(self):
self.balance = 100000
def balance(self):
self.balance
def whitdraw(self, amount):
self.balance -= amount
... | My version of your code, with comments:
```
#
# 1. CamelCasing for classes
#
class Account:
def __init__(self):
# 2. to refer to the inner class, you must use self.Bank
# 3. no need to use an inner class here
self.bank = self.Bank()
class Bank:
def __init__(self):
s... |
What does "\r" do in the following script? | 14,606,799 | 8 | 2013-01-30T14:51:05Z | 14,606,871 | 10 | 2013-01-30T14:54:37Z | [
"python",
"telnet"
] | I am using following script to reboot my router using Telnet:
```
#!/usr/bin/env python
import os
import telnetlib
from time import sleep
host = "192.168.1.1"
user = "USER"
password = "PASSWORD"
cmd = "system restart"
tn = telnetlib.Telnet(host)
sleep(1)
tn.read_until("Login: ")
tn.write(user + "\n\r")
sleep(1)
t... | The `'\r'` character is the carriage return, and the carriage return-newline pair is both needed for newline in a network virtual terminal session.
---
From the [old telnet specification (RFC 854)](https://tools.ietf.org/html/rfc854) (page 11):
> The sequence "CR LF", as defined, will cause the NVT to be
> positione... |
How to properly convert list of one element to a tuple with one element | 14,607,128 | 4 | 2013-01-30T15:07:00Z | 14,607,155 | 12 | 2013-01-30T15:08:18Z | [
"python",
"python-2.6"
] | ```
>>> list=['Hello']
>>> tuple(list)
('Hello',)
```
Why is the result of the above statements `('Hello',)` and not `('Hello')`?. I would have expected it to be the later. | You've got it right. In python if you do:
```
a = ("hello")
```
`a` will be a string since the parenthesis in this context are used for grouping things together. It is actually the comma which makes a tuple, not the parenthesis (parenthesis are just needed to avoid ambiguity in certain situations like function calls)... |
How to debug code that never stops running? | 14,607,876 | 2 | 2013-01-30T15:41:29Z | 14,608,049 | 7 | 2013-01-30T15:48:56Z | [
"python",
"python-2.7"
] | I have a large code base, and something is now taking too long to execute. I have no idea what.
The code never raises an exception, it just appears to keep on processing something.
What I'd like to do is place timers around some functions to test which one is the culprit. But I'm not sure if that is the right approac... | One solution is to use `cProfile`, which comes built into Python, to tell what functions your code is spending the most time in. Critically, this profiling works *even if you stop your code with a* `KeyboardInterrupt`. Thus, you can start your code running and profiling, stop it after a minute or two, and then see wher... |
How to check if a specific integer is in a list | 14,608,015 | 2 | 2013-01-30T15:47:20Z | 14,608,067 | 11 | 2013-01-30T15:49:49Z | [
"python",
"list",
"if-statement",
"python-2.7",
"int"
] | I want to know how to make an if statement that executes a clause if a certain integer is in a list.
All the other answers I've seen ask for a specific condition like prime numbers, duplicates, etc. and I could not glean the solution to my problem from the others. | You could simply use the `in` keyword. Like this :
```
if number_you_are_looking_for in list:
# your code here
```
For instance :
```
myList = [1,2,3,4,5]
if 3 in myList:
print("3 is present")
``` |
Python 3: Change default values of existing function's parameters? | 14,608,908 | 8 | 2013-01-30T16:30:19Z | 14,608,958 | 12 | 2013-01-30T16:32:54Z | [
"python",
"parameters",
"python-3.x",
"arguments",
"default"
] | I'm creating a program which will eventually have like 500 calls for `print` function, and some others too. Each of these functions will take the exact same parameters every time, like this:
```
print(a, end='-', sep='.')
print(b, end='-', sep='.')
print(c, end='-', sep='.')
print(..., end='-', sep='.')
```
Is there ... | You can define a special version of `print()` using [`functools.partial()`](http://docs.python.org/3/library/functools.html#functools.partial) to give it default arguments:
```
from functools import partial
myprint = partial(print, end='-', sep='.')
```
and `myprint()` will then use those defaults throughout your co... |
Python first and last element from array | 14,609,720 | 11 | 2013-01-30T17:10:18Z | 14,609,801 | 11 | 2013-01-30T17:14:07Z | [
"python",
"arrays",
"numpy"
] | I am trying to dynamically get the first and last element from an array.
So, let us suppose the array has 6 elements.
```
test = [1,23,4,6,7,8]
```
If I am trying to get the `first and last = 1,8`, `23,7` and `4,6`. Is there a way to get elements in this order?
I looked at a couple of questions [Link](http://stackov... | How about:
```
In [10]: arr = numpy.array([1,23,4,6,7,8])
In [11]: [(arr[i], arr[-i-1]) for i in range(len(arr) // 2)]
Out[11]: [(1, 8), (23, 7), (4, 6)]
```
Depending on the size of `arr`, writing the entire thing in NumPy may be more performant:
```
In [41]: arr = numpy.array([1,23,4,6,7,8]*100)
In [42]: %timeit... |
Python first and last element from array | 14,609,720 | 11 | 2013-01-30T17:10:18Z | 21,169,102 | 30 | 2014-01-16T17:46:15Z | [
"python",
"arrays",
"numpy"
] | I am trying to dynamically get the first and last element from an array.
So, let us suppose the array has 6 elements.
```
test = [1,23,4,6,7,8]
```
If I am trying to get the `first and last = 1,8`, `23,7` and `4,6`. Is there a way to get elements in this order?
I looked at a couple of questions [Link](http://stackov... | I ended here, because I googled for "python first and last element of array", and found everything else but this. So here's the answer to the title question:
```
a = [1,2,3]
a[0] # first element (returns 1)
a[-1] # last element (returns 3)
``` |
Unreliable results with cv2.HoughCircles | 14,609,980 | 8 | 2013-01-30T17:23:44Z | 14,615,347 | 11 | 2013-01-30T22:46:58Z | [
"python",
"image-processing",
"opencv"
] | I have a video with 5 oil droplets, and I am trying to use cv2.HoughCircles to find them.
This is my code:
```
import cv, cv2
import numpy as np
foreground1 = cv2.imread("foreground1.jpg")
vid = cv2.VideoCapture("NB14.avi")
cv2.namedWindow("video")
cv2.namedWindow("canny")
cv2.namedWindow("blur")
while True:
r... | Initially I though there would be no overlapping in your oil droplets, but there are. So, Hough might indeed by a good method to use here, but I've had better experience when combining RANSAC with it. I would suggest exploring that, but here I will provide something different from that.
First of all, I couldn't perfor... |
How can I process a python dictionary with callables? | 14,610,346 | 5 | 2013-01-30T17:43:18Z | 14,610,441 | 8 | 2013-01-30T17:48:53Z | [
"python",
"dictionary"
] | I would like to create a python directory whose values are to be evaluated separately.
So, for example, in the following non-working example I define
```
a = {'key1': 'value1', 'key2': 42, 'key3': foo(20)}
```
for which e.g.
```
def foo(max):
"""Returns random float between 0 and max."""
return max*random.r... | Use the [`functools.partial()`](http://docs.python.org/2/library/functools.html#functools.partial) to create a callable that'll apply a set of arguments to another callable:
```
from functools import partial
a = {'key1': 'value1', 'key2': 42, 'key3': partial(foo, 20)}
```
Now the `key3` value is a callable object; `... |
How to connect to Facebook Graph API from Python using Requests if I do not need user access token? | 14,611,240 | 6 | 2013-01-30T18:34:23Z | 14,626,170 | 9 | 2013-01-31T12:47:03Z | [
"python",
"facebook-graph-api",
"python-requests"
] | I am trying to find the easiest way how to use Facebook Graph API using my favorite [Requests](http://docs.python-requests.org/) library. The problem is, all examples I found are about getting **user access token**, about redirects and user interaction.
All I need is only **application access token**. I do not handle ... | Following <https://developers.facebook.com/docs/technical-guides/opengraph/publishing-with-app-token/>:
```
import requests
r = requests.get('https://graph.facebook.com/oauth/access_token?grant_type=client_credentials&client_id=123&client_secret=XXX')
access_token = r.text.split('=')[1]
print access_token
```
(using ... |
Malformed String ValueError ast.literal_eval() with String representation of Tuple | 14,611,352 | 19 | 2013-01-30T18:41:06Z | 14,611,535 | 12 | 2013-01-30T18:51:24Z | [
"python",
"parsing",
"python-2.x",
"abstract-syntax-tree",
"representation"
] | I'm trying to read in a string representation of a Tuple from a file, and add the tuple to a list. Here's the relevant code.
```
raw_data = userfile.read().split('\n')
for a in raw_data :
print a
btc_history.append(ast.literal_eval(a))
```
Here is the output:
```
(Decimal('11.66985'), Decimal('0E-8'))
Trace... | From the [documentation](http://docs.python.org/2/library/ast.html#ast.literal_eval) for `ast.literal_eval()`:
> Safely evaluate an expression node or a string containing a Python expression. **The string or node provided may only consist of the following Python literal structures: strings, numbers, tuples, lists, dic... |
Malformed String ValueError ast.literal_eval() with String representation of Tuple | 14,611,352 | 19 | 2013-01-30T18:41:06Z | 18,178,379 | 21 | 2013-08-12T01:25:15Z | [
"python",
"parsing",
"python-2.x",
"abstract-syntax-tree",
"representation"
] | I'm trying to read in a string representation of a Tuple from a file, and add the tuple to a list. Here's the relevant code.
```
raw_data = userfile.read().split('\n')
for a in raw_data :
print a
btc_history.append(ast.literal_eval(a))
```
Here is the output:
```
(Decimal('11.66985'), Decimal('0E-8'))
Trace... | `ast.literal_eval` (located in `ast.py`) parses the tree with `ast.parse` first, then it evaluates the code with quite an ugly recursive function, interpreting the parse tree elements and replacing them with their literal equivalents. Unfortunately the code is not at all expandable, so to add `Decimal` to the code you ... |
Why is this flask-admin form alway failing validation? | 14,611,374 | 4 | 2013-01-30T18:42:23Z | 14,612,624 | 11 | 2013-01-30T20:01:19Z | [
"python",
"sqlalchemy",
"flask",
"wtforms"
] | The status field shows the 3 options, but always displays "Not a valid choice" on submisison, whichever is chosen.
```
from website import app, db
from flask.ext import admin
from flask.ext.admin.contrib import sqlamodel
from wtforms.fields import SelectField
class Users(db.Model):
id = db.Column(db.Integer,... | It is likely that the choices are being sent as unicode string while your status field in db is integer. Can you try the following:
```
form_args = dict(
status=dict(
choices=[(0, 'Regular'), (1, 'Guest'), (2, 'Banned')],coerce=int
))
``` |
Selenium not deleting profiles on browser close | 14,612,294 | 3 | 2013-01-30T19:41:18Z | 14,612,967 | 7 | 2013-01-30T20:22:13Z | [
"python",
"firefox",
"selenium"
] | I'm running some fairly simple tests using browsermob and selenium to open firefox browsers and navigate through a random pages. Each firefox instance is supposed to be independent and none of them share any cookies or cache. On my mac osx machine, this works quite nicely. The browsers open, navigate through a bunch of... | On your mac, have you looked in /var/folders/? You might find a bunch of anonymous\*webdriver-profile folders a few levels down. (mine appear in /var/folders/sm/jngvd6s57ldb916b7h25d57r0000dn/T/)
Also, are you using driver.close() or driver.quit()? I thought driver.quit() cleans up the temp folder, but I could be wron... |
Memcached: auto-discovery python support on AWS Elasticache? | 14,612,632 | 6 | 2013-01-30T20:01:34Z | 22,107,561 | 7 | 2014-02-28T23:11:20Z | [
"python",
"django",
"caching",
"memcached"
] | I started to use AWS Elasticache with my django web app.
I started by setting the cache location to the unique endpoint using the auto-discovery feature, but it doesn't seems to work.
I'm using pylibmc (1.2.2) and django-pylibmc-sasl (0.2.4) to connect to memcached from python.
Does the auto-discovery feature work o... | # Quick answer
Yes for django: [django-elasticache](https://github.com/gusdan/django-elasticache)
## Long Answer
ElastiCache provides memcached interface so there are three solution of using it:
## 1. Memcached configured with location = Configuration Endpoint.
In this case your application
will randomly connect t... |
Plotting distance arrows in technical drawing | 14,612,637 | 13 | 2013-01-30T20:01:52Z | 14,613,143 | 8 | 2013-01-30T20:31:15Z | [
"python",
"matplotlib"
] | I want to indicate a distance in one of my plots. What I have in mind is the way they do it in technical drawings, showing a double headed arrow with the distance as text beside it.
**Example:**
```
from matplotlib.pyplot import *
hlines(7,0,2, linestyles='dashed')
hlines(11,0,2, linestyles='dashed')
hlines(10,0,2, ... | Try using `annotate`:
```
annotate ('', (0.4, 0.2), (0.4, 0.8), arrowprops={'arrowstyle':'<->'})
```
I'm not sure about automatic text placement though. |
Plotting distance arrows in technical drawing | 14,612,637 | 13 | 2013-01-30T20:01:52Z | 14,613,257 | 16 | 2013-01-30T20:37:20Z | [
"python",
"matplotlib"
] | I want to indicate a distance in one of my plots. What I have in mind is the way they do it in technical drawings, showing a double headed arrow with the distance as text beside it.
**Example:**
```
from matplotlib.pyplot import *
hlines(7,0,2, linestyles='dashed')
hlines(11,0,2, linestyles='dashed')
hlines(10,0,2, ... | ```
import matplotlib.pyplot as plt
plt.hlines(7, 0, 2, linestyles='dashed')
plt.hlines(11, 0, 2, linestyles='dashed')
plt.hlines(10, 0, 2, linestyles='dashed')
plt.hlines(8, 0, 2, linestyles='dashed')
plt.annotate(
'', xy=(1, 10), xycoords='data',
xytext=(1, 8), textcoords='data',
arrowprops={'arrowstyle'... |
python os library source code location | 14,613,223 | 4 | 2013-01-30T20:35:28Z | 14,613,405 | 8 | 2013-01-30T20:45:00Z | [
"python"
] | I'm in learning mode --- this is probably a dumb or rtfm question but here it is:
Where is the source code for the Python os library located? I've downloaded the Python tarball. Lots of usages in there but can't seem to find the source code itself and how it hooks into the OS. I'm interested in seeing what's done for t... | `os`'s implementation is scattered across a number of files.
The core C functions are mostly located in [Modules/posixmodule.c](http://hg.python.org/cpython/file/v2.7.3/Modules/posixmodule.c), which, despite its name, contains implementations for OS routines on Windows NT and OS/2, in addition to POSIX routines.
Wrap... |
merging two tables with millions of rows in python | 14,614,512 | 8 | 2013-01-30T21:51:56Z | 14,617,925 | 12 | 2013-01-31T03:24:35Z | [
"python",
"join",
"merge",
"pandas",
"pytables"
] | I am using python for some data analysis. I have two tables, the first (lets call it 'A') has 10 million rows and 10 columns and the second ('B') has 73 million rows and 2 columns. They have 1 column with common ids and I want to intersect the two tables based on that column. In particular I want the inner join of the ... | this is a little pseudo codish, but I think should be quite fast.
straightfoward disk based merge, with all tables on disk. The
key is that you are not doing selection per se, just indexing
into the table via start/stop, which is quite fast.
Selecting the rows that meet a criteria in B (using A's ids) won't
be very fa... |
Why does communicate deadlock when used with multiple Popen subprocesses? | 14,615,462 | 7 | 2013-01-30T22:57:32Z | 14,617,026 | 8 | 2013-01-31T01:32:18Z | [
"python",
"python-2.7",
"multiprocessing",
"subprocess"
] | The following issue does *not* occur in Python 2.7.3. However, it occurs with both Python 2.7.1 and Python 2.6 on my machine (64-bit Mac OSX 10.7.3). This is code I will eventually distribute, so I would like to know if there is any way to complete this task that does not depend so dramatically on the Python version.
... | I had to dig a bit for this one. (I ran into a similar problem once, so thought I knew the answer, but was wrong.)
The issue (and patch for 2.7.3) is described here:
<http://bugs.python.org/issue12786>
The issue is that the PIPEs get inherited by subprocesses. The answer is to use 'close\_fds=True' in your Popen cal... |
How can VIM tell the difference between `Ctrl-J` and `LF`? | 14,615,717 | 6 | 2013-01-30T23:20:25Z | 14,619,214 | 9 | 2013-01-31T05:39:53Z | [
"python",
"vim",
"ncurses",
"python-curses"
] | I'm trying to create a little Python/curses app.
But as far as I can see there's no way to tell whether
`CTRL`+`J` or `Enter` have been pressed. Now this may be caused by the fact that they both have the same ascii code (10):
<http://en.wikipedia.org/wiki/Control_character#In_ASCII>
But how can VIM tell the differen... | `Enter` is usually equivalent to C-m. But, if the `icrnl` flag is active for the tty (see `stty -a`), then an input C-m will automatically be translated to C-j (so that it is easy to type Unix-ly terminated lines by just pressing `Enter`).
In plain C you could use the *termios* functions *tcgetattr(3)* and *tcsetattr(... |
Why won't Django use IPython? | 14,616,805 | 19 | 2013-01-31T01:05:29Z | 14,617,014 | 38 | 2013-01-31T01:31:14Z | [
"python",
"django",
"virtualenv",
"ipython"
] | ```
(myvenv)me:src orokusaki$ python manage.py shell -i ipython
Python 2.7.2 (default, Jun 16 2012, 12:38:40)
[GCC 4.2.1 Compatible Apple Clang 4.0 (tags/Apple/clang-418.0.60)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> while True:
... pass # :(
...
`... | Try installing it into virtualenv! :-) |
Why won't Django use IPython? | 14,616,805 | 19 | 2013-01-31T01:05:29Z | 20,043,174 | 12 | 2013-11-18T08:27:33Z | [
"python",
"django",
"virtualenv",
"ipython"
] | ```
(myvenv)me:src orokusaki$ python manage.py shell -i ipython
Python 2.7.2 (default, Jun 16 2012, 12:38:40)
[GCC 4.2.1 Compatible Apple Clang 4.0 (tags/Apple/clang-418.0.60)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> while True:
... pass # :(
...
`... | I love iPython but don't like installing it in all my virtualenvs, and I've found a good solution to allow for that. Instead of using `python manage.py shell`, you can just use the system iPython directly.
In order for this to work properly, you need to set the DJANGO\_SETTINGS\_MODULE so that it corresponds to your p... |
Why is pip installing an old version of my package? | 14,617,136 | 44 | 2013-01-31T01:46:33Z | 15,189,799 | 14 | 2013-03-03T19:25:42Z | [
"python",
"pip",
"setuptools"
] | I've just uploaded a new version of my package to PyPi (1.2.1.0-r4): I can download the egg file and install it with easy\_install, and the version checks out correctly. But when I try to install using pip, it installs version 1.1.0.0 instead. Even if I explicitly specify the version to pip with `pip install -Iv tome==... | I found [here](http://python.6.n6.nabble.com/using-pip-to-install-an-specific-older-version-td4679821.html) that there is a known bug in pip that it won't check the version if there's a build directory with unpacked sources. I have checked this on my troubling package and after deleting its sources from build directory... |
Why is pip installing an old version of my package? | 14,617,136 | 44 | 2013-01-31T01:46:33Z | 17,153,977 | 52 | 2013-06-17T18:09:27Z | [
"python",
"pip",
"setuptools"
] | I've just uploaded a new version of my package to PyPi (1.2.1.0-r4): I can download the egg file and install it with easy\_install, and the version checks out correctly. But when I try to install using pip, it installs version 1.1.0.0 instead. Even if I explicitly specify the version to pip with `pip install -Iv tome==... | This is an excellent question. It took me forever to figure out. This is the solution that works for me:
Apparently, if `pip` can find a local version of the package, `pip` will prefer the local versions to remote ones. I even disconnected my computer from the internet and tried it again -- when `pip` still installed ... |
Why is pip installing an old version of my package? | 14,617,136 | 44 | 2013-01-31T01:46:33Z | 18,105,975 | 16 | 2013-08-07T14:22:25Z | [
"python",
"pip",
"setuptools"
] | I've just uploaded a new version of my package to PyPi (1.2.1.0-r4): I can download the egg file and install it with easy\_install, and the version checks out correctly. But when I try to install using pip, it installs version 1.1.0.0 instead. Even if I explicitly specify the version to pip with `pip install -Iv tome==... | Thanks to [Marcus Smith](https://github.com/qwcode), who does amazing work as a maintener of pip, this was fixed in version 1.4 of pip which was released on 2013-07-23.
Relevant information from the [changelog](http://www.pip-installer.org/en/latest/news.html#changelog) for this version
> Fixed a number of issues (#4... |
RFCOMM without pairing using PyBluez on Debian? | 14,618,277 | 14 | 2013-01-31T04:05:10Z | 14,827,036 | 15 | 2013-02-12T06:51:55Z | [
"python",
"bluetooth",
"rfcomm",
"bluez"
] | I am trying to create an RFCOMM server process with Python that can be used without the need for pairing. Initially, I grabbed the two example scripts from the PyBluez documentation:
Server:
```
# file: rfcomm-server.py
# auth: Albert Huang <albert@csail.mit.edu>
# desc: simple demonstration of a server application ... | This turned out to be a problem with the Debian Squeeze bluez default configuration.
If anyone else hits this problem, disable the pnat plugin by editing /etc/bluetooth/main.conf:
```
DisablePlugins = pnat
```
Then restart bluetoothd.
```
$ sudo invoke-rc.d bluetooth restart
```
No changes were required to the PyB... |
python inserting variable string as file name | 14,622,314 | 5 | 2013-01-31T09:25:56Z | 14,622,351 | 18 | 2013-01-31T09:27:34Z | [
"python",
"file",
"python-2.7"
] | I'm trying to create a file file a unique file name, every time my script is ran, it's only intended to be weekly or monthly. so I chose to use the date for the file name.
```
f = open('%s.csv', 'wb') %name
```
is where I'm getting this error.
```
Traceback (most recent call last):
File "C:\Users\User\workspace\new3... | You need to put `% name` straight after the string:
```
f = open('%s.csv' % name, 'wb')
```
The reason your code doesn't work is because you are trying to `%` a file, which isn't string formatting, and is also invalid. |
Google BigQuery, create a table from a query result | 14,622,526 | 13 | 2013-01-31T09:36:18Z | 14,634,697 | 12 | 2013-01-31T20:38:00Z | [
"python",
"google-app-engine",
"google-bigquery"
] | ok, so we're using [Google BigQuery](https://developers.google.com/bigquery/) via python **API**,
my question is **how** to **create a table** (new one or overwrite old one) **from a query results** ? Some docs are [here](https://developers.google.com/bigquery/docs/queries), but I can't find it usefull.
basically, we ... | You can do this by specifying a destination table in the query. You would need to use the Jobs.insert api rather than the Jobs.query call, and you should specify writeDisposition=WRITE\_APPEND and fill out the destination table.
Here is what the configuration would look like, if you were using the raw api. If you're u... |
Customize sphinxdoc theme | 14,622,698 | 2 | 2013-01-31T09:45:41Z | 24,932,178 | 7 | 2014-07-24T11:15:19Z | [
"python",
"themes",
"python-sphinx"
] | Is there an easy way to customize the existing `sphinxdoc` theme? For the default theme, there are many theme-attributes, but in sphinxdoc I can't even set a logo or change some colors?
Or can you recommend my a site where I can learn how to modify themes? | All I wanted is to add [ReST strikethrough](http://stackoverflow.com/q/6518788/2923406) in my sphinx doc. Here is how I did it:
```
$ cd my-sphinx-dir
$ mkdir -p theme/static
$ touch theme/theme.conf
$ touch theme/static/style.css
```
In `theme/theme.conf`:
```
[theme]
inherit = default
stylesheet = style.css
pygmen... |
Mongoengine - How to perform a "save new item or increment counter" operation? | 14,623,430 | 5 | 2013-01-31T10:21:21Z | 14,623,777 | 9 | 2013-01-31T10:39:34Z | [
"python",
"mongodb",
"mongoengine"
] | I'm using MongoEngine in a web-scraping project. I would like to keep track of all the images I've encountered on all the scraped webpages.
To do so, I store the image `src` URL and the number of times the image has been encountered.
The MongoEngine model definition is the following:
```
class ImagesUrl(Document):
... | You should be able to just do an [upsert](https://mongoengine-odm.readthedocs.org/en/latest/apireference.html?highlight=upsert#mongoengine.queryset.QuerySet.update_one) eg:
```
ImagesUrl.objects(src=self.src).update_one(
upsert=True,
inc__counter=1,... |
boto encryption key with amazon s3 | 14,624,104 | 4 | 2013-01-31T10:58:48Z | 14,624,505 | 9 | 2013-01-31T11:19:57Z | [
"python",
"amazon-s3",
"boto"
] | As I see there with the function calls `set_contents_with_filename` or `set_contents_with_file`, I can set encryption to true and while in s3, it stays encrypted
I have some questions
1. If possible, I want to know, which is the key that is being used to encrypt the file.
2. If encryption is set to true, the encrypti... | The two functions you probably mean are [set\_contents\_from\_filename](http://boto.cloudhackers.com/en/latest/ref/s3.html#boto.s3.key.Key.set_contents_from_filename) and [set\_contents\_from\_file](http://boto.cloudhackers.com/en/latest/ref/s3.html#boto.s3.key.Key.set_contents_from_file)
> If possible, I want to know... |
What does a "version file" look like? | 14,624,245 | 14 | 2013-01-31T11:06:35Z | 14,626,175 | 13 | 2013-01-31T12:47:28Z | [
"python",
"windows",
"pyinstaller"
] | I've been googling this for ages now without results. The [PyInstaller](http://www.pyinstaller.org) manual says:
```
--version-file=FILE
add a version resource from FILE to the exe
```
That sounds nice. I want to put version information in my executables. The problem is that I have no clue what a "version file" l... | Just had a quick look at the sources. It appears that the version file is expected to be Python source itself as the provided version file with be read and then `eval`'ed.
The `GrabVersion.py` script appears to generate errors as you've already found, so I modified the `__repr__` function of `FixedFileInfo` to manuall... |
Pip packages not found - Brewed Python | 14,624,757 | 18 | 2013-01-31T11:34:14Z | 14,739,278 | 32 | 2013-02-06T21:37:27Z | [
"python",
"osx",
"virtualenv",
"pip",
"homebrew"
] | Running Python 2.7.3, installed with HomeBrew, on a mac.
Installed several packages using PIP, including virtualenv. (Using virtualenv as an example, but NONE of the packages work.)
When I try to run them in terminal, it fails as follows:
```
$ virtualenv venv --distribute
-bash: virtualenv: command not found
```
A... | The problem was that I had not added Python to the system $PATH.
At the end of the brew install it says (viewable by typing `brew info python`):
```
Executable python scripts will be put in:
/usr/local/share/python
so you may want to put "/usr/local/share/python" in your PATH, too.
```
So, simply had to open .p... |
Find http:// and or www. and strip from domain. leaving domain.com | 14,625,693 | 6 | 2013-01-31T12:22:07Z | 14,625,862 | 11 | 2013-01-31T12:31:11Z | [
"python",
"url",
"urlparse"
] | I'm quite new to python. I'm trying to parse a file of URLs to leave only the domain name.
some of the urls in my log file begin with http:// and some begin with www.Some begin with both.
This is the part of my code which strips the http:// part. What do I need to add to it to look for both http and www. and remove b... | It might be overkill for this specific situation, but i'd generally use [`urlparse.urlsplit`](http://docs.python.org/2/library/urlparse.html#urlparse.urlsplit) (Python 2) or [`urllib.parse.urlsplit`](http://docs.python.org/3.3/library/urllib.parse.html?highlight=urllib.parse#urllib.parse.urlsplit) (Python 3).
```
from... |
Inheritance best practice : *args, **kwargs or explicitly specifying parameters | 14,626,279 | 26 | 2013-01-31T12:52:45Z | 14,626,574 | 12 | 2013-01-31T13:10:23Z | [
"python",
"inheritance",
"method-signature"
] | I often find myself overwriting methods of a parent class, and can never decide if I should explicitly list given parameters or just use a blanket `*args, **kwargs` construct. Is one version better than the other? Is there a best practice? What (dis-)advantages am I missing?
```
class Parent(object):
def save(sel... | My choice would be:
```
class Child(Parent):
def save(self, commit=True, **kwargs):
super(Child, self).save(commit, **kwargs)
# more logic
```
It avoids accessing commit argument from `*args` and `**kwargs` and it keeps things safe if the signature of `Parent:save` changes (for example adding a n... |
Inheritance best practice : *args, **kwargs or explicitly specifying parameters | 14,626,279 | 26 | 2013-01-31T12:52:45Z | 14,770,951 | 18 | 2013-02-08T10:54:06Z | [
"python",
"inheritance",
"method-signature"
] | I often find myself overwriting methods of a parent class, and can never decide if I should explicitly list given parameters or just use a blanket `*args, **kwargs` construct. Is one version better than the other? Is there a best practice? What (dis-)advantages am I missing?
```
class Parent(object):
def save(sel... | **Liskov Substitution Principle**
Generally you don't want you method signature to vary in derived types. This can cause problems if you want to swap the use of derived types. This is often referred to as the [Liskov Substitution Principle](http://en.wikipedia.org/wiki/Liskov_substitution_principle).
**Benefits of Ex... |
pandas: HTML output with conditional formatting | 14,627,380 | 21 | 2013-01-31T13:52:00Z | 14,630,250 | 18 | 2013-01-31T16:16:27Z | [
"python",
"html",
"css",
"dataframe",
"pandas"
] | I am trying to format a table, such that data in each column are formatted in a style depending on their values (similar to conditional formatting in spreadsheet programs). How can I achieve that in pandas using the HTML formatter?
A typical use case is highlighting significant values in a table. For example:
```
... | You can use the DataFrame [`to_html`](http://pandas.pydata.org/pandas-docs/dev/generated/pandas.DataFrame.to_html.html) method, which comes with `formatters` argument.
*An easier solution would be to surround by `<span class="significant">` and `</span>`, (rather than `*`). Note: by default this will be escaped (i.e. ... |
Largest Eigenvector and possible Scipy weirdness | 14,627,475 | 3 | 2013-01-31T13:56:36Z | 14,627,916 | 7 | 2013-01-31T14:18:14Z | [
"python",
"scipy",
"eigenvector",
"eigenvalue"
] | Not sure whether this is a bug in the package or due to some other cause, but here we go.
I'm using the following package to find the largest eigenvalue and its corresponding eigenvector over a symmetric matrix of similarity scores (10x10 in size):
```
scipy.sparse.linalg.eigen.arpack.eigsh
```
, like so:
```
scipy... | This is actually a math question.
But the reason is that there's an arbitrary phase when you calculate eigenvectors. You're solving Ax = bx for x. The equation is invariant under multiplication by a (possibly ocmplex) phase.
As to why it happens in a (seemingly) random fashion, I don't know. But I'm pretty sure it's ... |
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