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 |
|---|---|---|---|---|---|---|---|---|---|
Counting bigrams (pair of two words) in a file using python | 12,488,722 | 8 | 2012-09-19T04:44:40Z | 12,488,794 | 23 | 2012-09-19T04:54:53Z | [
"python",
"regex"
] | I want to count the number of occurrences of all bigrams (pair of adjacent words) in a file using python. Here, I am dealing with very large files, so I am looking for an efficient way. I tried using count method with regex "\w+\s\w+" on file contents, but it did not prove to be efficient.
e.g. Let's say I want to cou... | Some `itertools` magic:
```
>>> import re
>>> from itertools import islice, izip
>>> words = re.findall("\w+",
"the quick person did not realize his speed and the quick person bumped")
>>> print Counter(izip(words, islice(words, 1, None)))
```
Output:
```
Counter({('the', 'quick'): 2, ('quick', 'person'): 2, ('p... |
How can I save this matplotlib figure such that the x-axis labels are not cropped out? | 12,490,657 | 4 | 2012-09-19T08:00:10Z | 12,491,287 | 9 | 2012-09-19T08:49:25Z | [
"python",
"matplotlib",
"pandas"
] | I am running the following snippet of code in the ipython notebook, using the `pandas` data analysis library along with `matplotlib.pyplot`.
```
titles = {'gradStat_p3': "P3: Gradiometers", 'magStat_p3': "P3: Magnetometers",
'gradStat_mmn': "MMN: Gradiometers", 'magStat_mmn': "MMN: Magnetometers"}
scale... | You can use fig.tight\_layout().
```
fig, ax = subplots(1,1,1)
ax.plot(np.random.randn(5))
ax.set_xticklabels(['this is a very long label', 'b', 'c', 'd', 'e'], rotation=90)
fig.tight_layout()
fig.savefig('test.pdf')
``` |
python distutils not include the SWIG generated module | 12,491,328 | 15 | 2012-09-19T08:52:23Z | 21,236,111 | 8 | 2014-01-20T14:08:09Z | [
"c++",
"python",
"swig",
"rpm",
"distutils"
] | I am using distutils to create an rpm from my project. I have this directory tree:
```
project/
my_module/
data/file.dat
my_module1.py
my_module2.py
src/
header1.h
header2.h
ext_module1.cpp
ext_module2.cp... | The problem is that `build_py` (which copies python sources to the build directory) comes before `build_ext`, which runs SWIG.
You can easily subclass the build command and swap around the order, so `build_ext` produces `module1.py` before `build_py` tries to copy it.
```
from distutils.command.build import build
cl... |
Splitting a string into 2-letter segments | 12,491,537 | 5 | 2012-09-19T09:04:00Z | 12,491,575 | 13 | 2012-09-19T09:06:38Z | [
"python",
"string",
"python-3.x",
"iterator"
] | I have a string, which I need to split into 2-letter pieces. For example, `'ABCDXY'` should become `['AB', 'CD', 'XY']`. The behavior in the case of odd number of characters may be entirely arbitrary (I'll check the length in advance).
Is there any way to do this without an ugly loop? | ```
>>> [s[i:i + 2] for i in range(0, len(s), 2)]
['AB', 'CD', 'XY']
``` |
Splitting a string into 2-letter segments | 12,491,537 | 5 | 2012-09-19T09:04:00Z | 12,491,676 | 15 | 2012-09-19T09:11:41Z | [
"python",
"string",
"python-3.x",
"iterator"
] | I have a string, which I need to split into 2-letter pieces. For example, `'ABCDXY'` should become `['AB', 'CD', 'XY']`. The behavior in the case of odd number of characters may be entirely arbitrary (I'll check the length in advance).
Is there any way to do this without an ugly loop? | Using regular expressions!
```
>>> import re
>>> s = "ABCDXYv"
>>> re.findall(r'.{1,2}',s,re.DOTALL)
['AB', 'CD', 'XY', 'v']
```
---
I know it has been a while, but I came back to this and was curious about which method was better; mine: `r'.{1,2}'` or Jon's `r'..?'`. On the surface, Jon's looks much nicer, and I th... |
Python sum of ASCII values of all characters in a string | 12,492,137 | 5 | 2012-09-19T09:39:11Z | 12,492,343 | 16 | 2012-09-19T09:51:00Z | [
"python",
"string",
"python-2.7",
"ascii"
] | I am searching a more efficient way to sum-up the [ASCII](http://en.wikipedia.org/wiki/ASCII) values of all characters in a given string, using only standard python (2.7 is preferable).
Currently I have:
```
print sum(ord(ch) for ch in text)
```
**I want to emphasize that my main focus and aspect of this question is... | You can use an intermediate `bytearray` to speed things up:
```
>>> sum(bytearray("abcdefgh"))
804
```
This is not 17 times faster than the generatorâit involves the creation of an intermediate `bytearray` and `sum` still has to iterate over Python integer objectsâbut on my machine it does speed up summing an 8-c... |
Decorators and class method | 12,493,074 | 18 | 2012-09-19T10:41:28Z | 12,493,278 | 14 | 2012-09-19T10:52:29Z | [
"python",
"class",
"methods",
"decorator"
] | I am having trouble understanding why the following happens. I am having a decorator which does nothing except it checks whether a function is a method. I thought I have understood what method in Python is, but obviously, this is not the case:
```
import inspect
def deco(f):
def g(*args):
print inspect.is... | Methods are functions that are associated with a class. Methods are only created when you retrieve them from an already defined class; a method is a wrapper around a function, with a reference to the class as well (and optionally a reference to the instance).
What happens in the first case is: Python compiles your cla... |
python syntax error with list filtering | 12,493,193 | 2 | 2012-09-19T10:47:03Z | 12,493,225 | 8 | 2012-09-19T10:49:15Z | [
"python"
] | I'm trying to filter an item from a list, and I'm getting a syntax error:
**SyntaxError: invalid syntax**
The code:
```
a['name'] = 'Dan'
b['name'] = 'Joe'
ppl = [a,b]
inputName = raw_input('Enter name:').strip()
person = [p in ppl if p['name']==inputName].pop()
```
any idea? | `[item for item in array]`
not
`[item in array]` |
Equivalent of the Scala IDE worksheet in other languages? | 12,495,318 | 9 | 2012-09-19T13:04:02Z | 12,495,693 | 10 | 2012-09-19T13:24:22Z | [
"java",
"python",
"ruby",
"ide"
] | > A worksheet is a Scala file that is evaluated on save, and the result of each expression is shown in a column to the right of your program. Worksheets are like a REPL session on steroids, and enjoy 1st class editor support: completion, hyperlinking, interactive errors-as-you-type, auto-format, etc. (source <https://g... | This is not really a language feature, more an IDE feature.
It looks like a pretty straightforward clone of the `Transcript` window which has been a standard part of Smalltalk IDEs since at the least the 1980s.
*One* of those Smalltalk IDEs is IBM VisualAge for Smalltalk (where it was called *Scrapbook*), which later... |
Sorting the catalog results by multiple fields | 12,495,813 | 4 | 2012-09-19T13:31:19Z | 12,495,894 | 7 | 2012-09-19T13:35:26Z | [
"python",
"plone"
] | I need to sort the catalog results by multiple fields.
In my case, first sort by year, then by month. The year and month field are included in my custom content type (`item_publication_year` and `item_publication_month` respectively).
However, I'm not getting the results that I want. The year and month are not ordere... | A better bet is to use the `key` parameter for sorting:
```
results.sort(key=lambda b: (b.item_publication_year, b.item_publication_month))
```
You can also use the [`sorted()` built-in function](http://docs.python.org/library/functions.html#sorted) instead of using `list()`; it'll return a sorted list for you, it's ... |
How can I override a constant in an imported Python module? | 12,496,089 | 6 | 2012-09-19T13:45:55Z | 12,496,239 | 9 | 2012-09-19T13:52:58Z | [
"python",
"module",
"python-import"
] | In my application I am using module within the package `example` called `examplemod`.
**My app:**
```
from example import examplemod
examplemod.do_stuff()
```
It imports another module within `example` like so.
**examplemod.py:**
```
from example import config
# uses config
# then does stuff
```
`config` uses a c... | Yes, but it'll only work as expected with fully qualified access paths to modules:
```
import example
example.examplemod.config.CONSTANT = "Better value"
example.examplemod.do_stuff()
``` |
Difference accessing element(s) of tuple and list | 12,496,435 | 3 | 2012-09-19T14:03:49Z | 12,496,458 | 14 | 2012-09-19T14:05:03Z | [
"python",
"list",
"tuples"
] | Why is there this difference accessing the element(s) of `t` when making it a `tuple`?
```
>>> t = [('ID','int')]
>>> for r in t:
print r
('ID', 'int')
t = (('ID','int'))
>>> for r in t:
print r
ID
int
```
I'd expect this to be exactly the same as the first example! Whereas populating the tuple with more than o... | `(('a', 'b'))` is the same as `('a', 'b')`.
You actually want `(('a', 'b'),)`
This is documented here:
> [**5.13. Expression lists**](http://docs.python.org/reference/expressions.html#grammar-token-expression_list)
>
> `expression_list ::= expression ( "," expression )* [","]`
>
> An expression list containing at le... |
Python evaluates 0 as False | 12,497,199 | 2 | 2012-09-19T14:48:35Z | 12,497,224 | 8 | 2012-09-19T14:49:49Z | [
"python",
"boolean"
] | In the Python console:
```
>>> a = 0
>>> if a:
... print "L"
...
>>> a = 1
>>> if a:
... print "L"
...
L
>>> a = 2
>>> if a:
... print "L"
...
L
```
Why does this happen? | 0 is a falsy value in python
Falsy values: [from (2.7) documentation:](http://docs.python.org/library/stdtypes.html#truth-value-testing)
> zero of any numeric type, for example, 0, 0L, 0.0, 0j. |
Python evaluates 0 as False | 12,497,199 | 2 | 2012-09-19T14:48:35Z | 12,497,466 | 8 | 2012-09-19T15:04:52Z | [
"python",
"boolean"
] | In the Python console:
```
>>> a = 0
>>> if a:
... print "L"
...
>>> a = 1
>>> if a:
... print "L"
...
L
>>> a = 2
>>> if a:
... print "L"
...
L
```
Why does this happen? | In Python, `bool` is a subclass of `int`, and `False` has the value `0`; even if values weren't implicitly cast to `bool` in an `if` statement (which they are), `False == 0` is true. |
python pandas: Remove duplicates by columns A, keeping the row with the highest value in column B | 12,497,402 | 31 | 2012-09-19T15:01:32Z | 13,059,751 | 52 | 2012-10-25T00:10:02Z | [
"python",
"duplicates",
"pandas"
] | I have a dataframe with repeat values in column A. I want to drop duplicates, keeping the row with the highest value in column B.
So this:
```
A B
1 10
1 20
2 30
2 40
3 10
```
Should turn into this:
```
A B
1 20
2 40
3 10
```
Wes has added some nice functionality to drop duplicates: <http://wesmckinney.com/blog/?p... | This takes the last. Not the maximum though:
```
In [10]: df.drop_duplicates(cols='A', take_last=True)
Out[10]:
A B
1 1 20
3 2 40
4 3 10
```
You can do also something like:
```
In [12]: df.groupby('A', group_keys=False).apply(lambda x: x.ix[x.B.idxmax()])
Out[12]:
A B
A
1 1 20
2 2 40
3 ... |
Dynamically building a Boolean expression | 12,497,917 | 6 | 2012-09-19T15:28:35Z | 12,497,972 | 9 | 2012-09-19T15:32:07Z | [
"python",
"boolean-expression"
] | I'm writing some code that increments the number at the end of a filename until it's no longer overwriting an existing file. I'm creating several files, all with the same base filename but different extensions, none of which I want to overwrite.
Naive version:
```
prefix = 'hello0'
while os.path.exists(prefix + '.abc... | You might want to use the `any()` built-in with a generator:
```
while any(os.path.exists(prefix + extension) for extension in extensions):
# then increment prefix and try again, as in your example code
```
This computes the `True` or `False` that you need with a simpler syntax.
In general, if I *ever* feel the... |
two level sorting of a list of dictionaries in python | 12,498,134 | 2 | 2012-09-19T15:40:49Z | 12,498,161 | 8 | 2012-09-19T15:42:24Z | [
"python",
"sorting"
] | I have a list of dictionaries as follows:
```
{"id": 1, "score": some_score.. othe values}
{"id": 1, "score": some_differetscore.. othe values}
{"id": 22, "score": some_score.. othe values}
{"id": 3, "score": some_score.. othe values}
```
What I am hoping to get is to iterate thru this list in such a way that i... | Try this:
```
sorted(mylist, key=lambda d: (d["id"], -d["score"]))
``` |
Install MySQL-python in virtualenv on Windows 7 | 12,498,317 | 7 | 2012-09-19T15:50:46Z | 15,209,295 | 18 | 2013-03-04T19:17:40Z | [
"python",
"python-2.7",
"virtualenv",
"pip",
"mysql-python"
] | I'm trying to install MySQL-python in my virtualenv (Windows 7 32b + Python 2.7.3), but unfortunately after command:
```
pip install MySQL-python
```
I get error message:
```
Install packages failed: Error occurred when installing package MySQL-python.
The following command was executed:
packaging_tool.py install... | Did you try using :
```
easy_install MySQL-python
```
It works for me in Windows 7 a long with Virtualenv. I had the same problem with pip. |
Install MySQL-python in virtualenv on Windows 7 | 12,498,317 | 7 | 2012-09-19T15:50:46Z | 20,092,578 | 11 | 2013-11-20T09:54:50Z | [
"python",
"python-2.7",
"virtualenv",
"pip",
"mysql-python"
] | I'm trying to install MySQL-python in my virtualenv (Windows 7 32b + Python 2.7.3), but unfortunately after command:
```
pip install MySQL-python
```
I get error message:
```
Install packages failed: Error occurred when installing package MySQL-python.
The following command was executed:
packaging_tool.py install... | If you can install mysql-python globally (in C:/python27) from <http://www.lfd.uci.edu/~gohlke/pythonlibs/#mysql-python>
then you can copy paste the following files from "C:/python/lib/site-packages" to your virtual environment "/lib/site-packages"
1. MySQL\_python-1.2.4-py2.7.egg-info(folder)
2. MySQLdb(folder)
3. \... |
Can I set a header with python's SimpleHTTPServer? | 12,499,171 | 33 | 2012-09-19T16:42:39Z | 12,499,670 | 8 | 2012-09-19T17:15:00Z | [
"python",
"cross-domain",
"simplehttpserver"
] | I'm using `SimpleHTTPServer` to test some webpages I'm working on. It works great, however I need to do some cross-domain requests. That requires setting a `Access-Control-Allow-Origin` header with the domains the page is allowed to access.
Is there an easy way to set a header with SimpleHTTPServer and serve the origi... | I'd say there's no simple way of doing it, where simple means *"just add 1-2 lines that will write the additional header and keep the existing functionality"*. So, the best solution would be to subclass the `SimpleHTTPRequestHandler` class and re-implement the functionality, with the addition of the new header.
The pr... |
Can I set a header with python's SimpleHTTPServer? | 12,499,171 | 33 | 2012-09-19T16:42:39Z | 13,354,482 | 37 | 2012-11-13T01:42:37Z | [
"python",
"cross-domain",
"simplehttpserver"
] | I'm using `SimpleHTTPServer` to test some webpages I'm working on. It works great, however I need to do some cross-domain requests. That requires setting a `Access-Control-Allow-Origin` header with the domains the page is allowed to access.
Is there an easy way to set a header with SimpleHTTPServer and serve the origi... | This is a bit of a hack because it changes `end_headers()` behavior, but I think it's slightly better than copying and pasting the entire `SimpleHTTPServer.py` file.
My approach overrides `end_headers()` in a subclass and in it calls `send_my_headers()` followed by calling the superclass's `end_headers()`.
It's not 1... |
ctypes how to pass string from python to c++ function, and how to return string from c++ function to python | 12,500,069 | 3 | 2012-09-19T17:41:24Z | 12,500,326 | 11 | 2012-09-19T18:00:13Z | [
"c++",
"python",
"string",
"ctypes"
] | I want to call a c++ function from python, this c++ function takes char\* as parameter, and return string. Below is my code.
wrapper.cpp
```
#include <Python.h>
#include <string>
#include <iostream>
using namespace std;
extern "C"
string return_string(char* name){
cout<<strlen(name)<<endl;
cout<<name<<endl;... | This has nothing to do with ctypes; your C++ code is invalid in itself. You can't define an `extern "C"` function that returns a `string`.
In a quick test with a C++ program that uses the same library, it also prints garbage.
I also wrote a C program that defines something called `string` with the same layout as `std... |
Passing multple files with asterisk to python shell in Windows | 12,501,761 | 7 | 2012-09-19T19:43:50Z | 12,501,850 | 9 | 2012-09-19T19:49:54Z | [
"python",
"command-line",
"arguments"
] | I'm going through Google's Python exercises and I need to be able to do this from the command line:
```
python babynames.py --summaryfile baby*.html
```
Where `python` is the Python shell, `babynames.py` is the Python program, `--summaryfile` is an argument to be interpreted by my `babynames` program, and `baby*.html... | Windows' command interpreter does not expand wildcards as UNIX shells do before passing them to the executed program or script.
```
python.exe -c "import sys; print sys.argv[1:]" *.txt
```
Result:
```
['*.txt']
```
Solution: Use the `glob` module.
```
from glob import glob
from sys import argv
for filename in glo... |
Randomly select x number of items from class list in python | 12,501,956 | 5 | 2012-09-19T19:57:14Z | 12,502,001 | 9 | 2012-09-19T20:01:11Z | [
"python",
"list",
"class",
"random",
"jython"
] | In jython, I have a class of objects defined like this:
```
class Item:
def __init__(self, pid, aisle, bay, hits, qtyPerOrder):
self.pid = pid
self.aisle = int(aisle)
self.bay = bay
self.hits = int(hits)
self.qtyPerOrder = int(qtyPerOrder)
```
I have created a class list called "list" of the ite... | You can use the [`random` module](http://www.jython.org/docs/library/random.html) to both pick a number between 3 and 20, and to take a sample of lines:
```
import random
sample_size = random.randint(3, 20)
sample = random.sample(yourlist, sample_size)
for item in sample:
print '%s, %d, %s, %d' % (item.pid, item... |
Python/numpy floating-point text precision | 12,502,122 | 2 | 2012-09-19T20:08:59Z | 12,502,750 | 7 | 2012-09-19T20:54:23Z | [
"python",
"numpy",
"floating-point",
"precision"
] | Let's say I have some 32-bit and 64-bit floating point values:
```
>>> import numpy as np
>>> v32 = np.array([5, 0.1, 2.4, 4.555555555555555, 12345678.92345678635],
dtype=np.float32)
>>> v64 = np.array([5, 0.1, 2.4, 4.555555555555555, 12345678.92345678635],
dtype=np.float64)
```... | Python 2.7 and later already have a smart `repr` implementation for floats that prints 0.1 as `0.1`. The brief output is chosen in preference to other candidates such as `0.10000000000000001` because it is the shortest representation of *that particular number* that roundtrips to the exact same floating-point value whe... |
Access Multiselect Form Field in Flask | 12,502,646 | 8 | 2012-09-19T20:46:15Z | 12,502,681 | 26 | 2012-09-19T20:49:13Z | [
"python",
"flask"
] | I have a multiselect in html file like this:
```
<select multiple id="mymultiselect" name="mymultiselect">
<option value="1">this</option>
<option value="2">that</option>
<option value="3">other thing</option>
</select>
```
When I access the mymultiselect field in flask/... | You want to use the [`getlist()` function](http://werkzeug.pocoo.org/docs/datastructures/#werkzeug.datastructures.MultiDict.getlist) to get a list of values:
```
multiselect = request.form.getlist('mymultiselect')
```
You do *not* need to add `[]` to the name to make this work; in fact, the `[]` will not help, don't ... |
Making a video with opencv and ffmpeg. How to find the right color format? | 12,503,368 | 10 | 2012-09-19T21:44:55Z | 12,573,365 | 13 | 2012-09-24T21:43:06Z | [
"python",
"opencv",
"image-processing",
"ffmpeg"
] | I have a webcam video recorder program built with python, opencv and ffmpeg
It works ok except that the color of the video is more blue than the reality. The problem seems to come from color format of images.
It seems that OpenCv is giving BGR images and ffmpeg+libx264 is expecting YUV420p. I've read that YUV420p cor... | You are right, the default pixel format of OpenCV is **BGR**.
The equivalent format on the ffmpeg side would be **BGR24**, so you don't need to convert it to YUV420p if you don't want to.
[This post](http://stackoverflow.com/a/5839058/176769) shows how to use a python application to capture frames from the webcam and... |
How to Reverse Hebrew String in Python? | 12,504,197 | 4 | 2012-09-19T23:19:38Z | 12,504,219 | 7 | 2012-09-19T23:22:49Z | [
"python"
] | I'm trying to reverse Hebrew string in Python:
```
line = '××××'
reversed = line[::-1]
print reversed
```
but I get:
```
UnicodeDecodeError: 'ascii' codec can't decode byte 0x93 in position 0: ordinal not in range(128)
```
Care to explain what I'm doing wrong?
EDIT: The answers are great, thanks!
I'm also tryi... | Adding `u` in front of the hebrew string works for me:
```
In [1]: line = u'××××'
In [2]: reversed = line[::-1]
In [2]: print reversed
××××
```
---
To your second question, you can use:
```
import codecs
w1 = codecs.open("~/fileName", "r", "utf-8")
w1.write(reversed)
```
To write unicode string to file ... |
How to handle DST and TZ in recurring events? | 12,504,247 | 9 | 2012-09-19T23:25:38Z | 12,527,753 | 9 | 2012-09-21T09:24:51Z | [
"python",
"datetime",
"pytz",
"rrule",
"python-dateutil"
] | Does dateutil rrule support DST and TZ? Need something similar to iCalendar RRULE.
If not - how to tackle this problem (scheduling recurring events & DST offset change)
Imports
```
>>> from django.utils import timezone
>>> import pytz
>>> from datetime import timedelta
>>> from dateutil import rrule
>>> now = timezo... | @asdf: I can't add code to comments so I need to post this as an answer:
I am afraid that with your solution I will always loose DST info, therefore half of the year recurrences would be 1 hour off time.
Basing on your answer I found out that this might be the correct solution:
```
>>> from datetime import datetime
... |
Adding pandas Series with different indices without getting NaNs | 12,504,493 | 9 | 2012-09-20T00:02:13Z | 12,504,527 | 18 | 2012-09-20T00:09:18Z | [
"python",
"pandas"
] | I'm trying to do what I think is a straight froward operation in pandas but I can't seem to make it work.
I have two pandas Series with different numbers of indices, I would like to add values together if they share an index, otherwise I would just like to pass the values that don't have corresponding indices along.
... | You could use `fill_value`:
```
>>> import pandas as pd
>>> Sr1 = pd.Series([1,2,3,4], index = ['A', 'B', 'C', 'D'])
>>> Sr2 = pd.Series([5,6], index = ['A', 'C'])
>>> Sr1+Sr2
A 6
B NaN
C 9
D NaN
>>> Sr1.add(Sr2, fill_value=0)
A 6
B 2
C 9
D 4
``` |
how to see Heroku logging and runtime error output in python | 12,504,588 | 5 | 2012-09-20T00:17:35Z | 12,877,333 | 11 | 2012-10-13T21:51:57Z | [
"python",
"web-applications",
"heroku"
] | I'm working on a web app in Python with Heroku and I can't figure out how to effectively test debug it. I tried using print(...) and sys.stdout.write(...) but I never see any output when I run locally with 'foreman start' or when I deploy to the cloud and run 'heroku logs' to see cloud logs. Furthermore, I can't figure... | Adding `sys.stdout.flush()` after print statements solved this problem for me.
In my case, the problem seemed to be that stdout is buffered whereas stderr is not.
If you're not even seeing exceptions via `foreman start`, make sure you're actually hitting your server at the right IP/PORT. You should see HTTP access en... |
how to see Heroku logging and runtime error output in python | 12,504,588 | 5 | 2012-09-20T00:17:35Z | 21,396,876 | 7 | 2014-01-28T04:33:19Z | [
"python",
"web-applications",
"heroku"
] | I'm working on a web app in Python with Heroku and I can't figure out how to effectively test debug it. I tried using print(...) and sys.stdout.write(...) but I never see any output when I run locally with 'foreman start' or when I deploy to the cloud and run 'heroku logs' to see cloud logs. Furthermore, I can't figure... | If you are using Foreman to run a Python project, and you're having trouble seeing stdout/stderr, here are some solutions for you. If you are using a Procfile to invoke the python CLI directly, then you can use the '-u' option to avoid stdout buffering:
```
python -u script.py
```
If you are using a Procfile to manag... |
Behavior of range in python and arange in numpy | 12,504,632 | 2 | 2012-09-20T00:23:50Z | 12,504,653 | 7 | 2012-09-20T00:26:59Z | [
"python",
"numpy",
"range"
] | Can someone please explain the '-5' below.
I'm somewhat new to numpy, but this seems bizarre
```
In [112]: an_int=9
In [113]: an_int/2
Out[113]: 4
In [114]: range(-an_int/2,an_int/2)
Out[114]: [-5, -4, -3, -2, -1, 0, 1, 2, 3]
In [115]: arange(-an_int/2,an_int/2)
Out[115]: array([-5, -4, -3, -2, -1, 0, 1, 2, 3])... | The problem isn't numpy. The "problem" is that integer division in python floors the result as opposed to truncating toward 0 (like the C language) -- e.g. `-9/2` *which is parsed as `(-9)/2`* (or `(-9)//2` if you're using python3.x) evaluates to `-5`. The builtin `int` function on the other hand does truncate toward z... |
Save session in IPython like in MATLAB? | 12,504,951 | 17 | 2012-09-20T01:20:19Z | 12,505,031 | 11 | 2012-09-20T01:34:06Z | [
"python",
"ipython",
"pandas"
] | It would be useful to save the session variables which could be loaded easily into memory at a later stage. | ```
In [23]: %logstart /tmp/session.log
Activating auto-logging. Current session state plus future input saved.
Filename : /tmp/session.log
Mode : backup
Output logging : False
Raw input log : False
Timestamping : False
State : active
In [24]: x = 1
In [25]: %logstop
In [26]: quit()
Do yo... |
Get last "column" after .str.split() operation on column in pandas DataFrame | 12,504,976 | 20 | 2012-09-20T01:24:57Z | 12,505,089 | 23 | 2012-09-20T01:43:43Z | [
"python",
"string",
"pandas",
"split"
] | I have a column in a pandas DataFrame that I would like to split on a single space. The splitting is simple enough with `DataFrame.str.split(' ')`, but I can't make a new column from the last entry. When I `.str.split()` the column I get a list of arrays and I don't know how to manipulate this to get a new column for m... | You could use the `tolist` method as an intermediary:
```
In [99]: import pandas as pd
In [100]: d1 = pd.DataFrame({'ticker' : ['spx 5/25/2001 p500', 'spx 5/25/2001 p600', 'spx 5/25/2001 p700']})
In [101]: d1.ticker.str.split().tolist()
Out[101]:
[['spx', '5/25/2001', 'p500'],
['spx', '5/25/2001', 'p600'],
['spx'... |
Get last "column" after .str.split() operation on column in pandas DataFrame | 12,504,976 | 20 | 2012-09-20T01:24:57Z | 13,053,267 | 26 | 2012-10-24T16:13:48Z | [
"python",
"string",
"pandas",
"split"
] | I have a column in a pandas DataFrame that I would like to split on a single space. The splitting is simple enough with `DataFrame.str.split(' ')`, but I can't make a new column from the last entry. When I `.str.split()` the column I get a list of arrays and I don't know how to manipulate this to get a new column for m... | Do this:
```
In [43]: temp2.str[-1]
Out[43]:
0 p500
1 p600
2 p700
Name: ticker
``` |
In Python, why doesn't an import in an exec in a function work? | 12,505,047 | 13 | 2012-09-20T01:36:18Z | 12,505,166 | 9 | 2012-09-20T01:54:10Z | [
"python",
"function",
"import",
"exec"
] | I can put an import statement in a string, exec it, and it works (prints a random digit):
```
code = """
import random
def f():
print random.randint(0,9)
"""
def f():
pass
exec code
f()
```
Now, if I put `exec code` and `f()` in their own function and call it, it doesn't work.
```
def test():
exec code... | What's going on here is that the module random is being imported as a local variable in test. Try this
```
def test():
exec code
print globals()
print locals()
f()
```
will print
```
{'code': '\nimport random\ndef f():\n print random.randint(0,9)\n', '__builtins__': <module '__builtin__' (built-in... |
Print not working when compiled with py2exe | 12,505,383 | 7 | 2012-09-20T02:33:36Z | 12,505,630 | 9 | 2012-09-20T03:16:13Z | [
"python",
"printing",
"py2exe"
] | this is my very simple code, printing argvs:
```
import sys
argv=sys.argv
for each in sys.argv:
print each
```
here's the output when ran:
```
e:\python>python test1.py 1 2 3 4 5
test1.py
1
2
3
4
5
```
I want it to be compiled, so I made one with py2exe:
```
e:\python>python setup.py py2exe
```
and my setup.... | ```
# ...
windows = [{'script': "test1.py"}],
#...
```
`windows` option is used to create GUI executables, which suppresses console output. Use `console` instead:
```
from distutils.core import setup
import py2exe, sys, os
sys.argv.append('py2exe')
setup(
options = {'py2exe': {'bundle_files': 3}},
console =... |
Python: Recommended way to walk complex dictionary structures imported from JSON? | 12,507,206 | 20 | 2012-09-20T06:36:47Z | 12,507,453 | 28 | 2012-09-20T06:58:40Z | [
"python",
"json",
"dictionary",
"python-2.7"
] | Importing from `JSON` can get very complex and nested structures.
For example:
```
{u'body': [{u'declarations': [{u'id': {u'name': u'i',
u'type': u'Identifier'},
u'init': {u'type': u'Literal', u'value': 2},
u'type': u'... | If you only need to walk the dictionary, I'd suggest using a recursive `walk` function that takes a dictionary and then recursively walks through its elements. Something like this:
```
def walk(node):
for key, item in node.items():
if item is a collection:
walk(item)
else:
I... |
Python: Recommended way to walk complex dictionary structures imported from JSON? | 12,507,206 | 20 | 2012-09-20T06:36:47Z | 12,507,546 | 16 | 2012-09-20T07:04:40Z | [
"python",
"json",
"dictionary",
"python-2.7"
] | Importing from `JSON` can get very complex and nested structures.
For example:
```
{u'body': [{u'declarations': [{u'id': {u'name': u'i',
u'type': u'Identifier'},
u'init': {u'type': u'Literal', u'value': 2},
u'type': u'... | You can use recursive generator for convert your dictionary to linear lists.
```
def dict_generator(indict, pre=None):
pre = pre[:] if pre else []
if isinstance(indict, dict):
for key, value in indict.items():
if isinstance(value, dict):
for d in dict_generator(value, [key] ... |
Determine empty template variable in Django | 12,507,281 | 5 | 2012-09-20T06:44:12Z | 17,307,803 | 17 | 2013-06-25T21:24:37Z | [
"python",
"django",
"mongodb",
"django-templates",
"pymongo"
] | I'm not able to determine whether a variable is empty when used in the template.
I've iterated through the whole collection and in each I'm looking for a variable `narrative_text`.
I tested the empty variable by
```
{% ifnotequal narratives.narrative_text '' %}
```
I notice the control enters this block, but prints ... | Pipe through length and do your test against that value.
```
{% if narratives.narrative_text|length > 0 %}
{{ narratives.narrative_text }}
{% else %}
None
{% endif %}
``` |
Error using knnMatch with OpenCV+Python | 12,508,934 | 6 | 2012-09-20T08:37:31Z | 12,554,234 | 7 | 2012-09-23T16:54:29Z | [
"python",
"opencv",
"runtime-error"
] | I want to match two pictures using Python+OpenCV. I have used SURF to extract keypoints and descriptors from both of them. Now, I need to match these descriptors and for this reason I decided to use Flann Matcher.
```
flann_params = dict(algorithm = FLANN_INDEX_KDTREE,trees = 4)
matcher = cv2.FlannBasedMatcher(fla... | I solved this problem using the correct data type with the function np.asarray()
```
raw_matches=matcher.knnMatch(np.asarray(desc1,np.float32),np.asarray(desc2,np.float32), 2) #2
``` |
How can I send an xml body using requests library? | 12,509,888 | 10 | 2012-09-20T09:37:56Z | 12,510,559 | 33 | 2012-09-20T10:17:12Z | [
"python",
"python-requests"
] | ```
def request():
#encoded_xml = urllib.urlencode({'XML': read_xml()})
#encoded_xml = read_xml()
headers = {'Authorization': AUTH_TOKEN,\
'developerToken': DEVELOPER_TOKEN,\
'clientCostumerID': CLIENT_ID}
content = {'__rdxml': encoded_xml}
#content = encoded_xml
#c... | Just send xml bytes directly:
```
# -*- coding: utf-8 -*-
import requests
xml = """<?xml version='1.0' encoding='utf-8'?>
<a>б</a>"""
headers = {'Content-Type': 'application/xml'} # set what your server accepts
print requests.post('http://httpbin.org/post', data=xml, headers=headers).text
```
### Output
```
{
"o... |
In gevent, how can I dump stack traces of all running greenlets? | 12,510,648 | 10 | 2012-09-20T10:22:35Z | 12,553,888 | 12 | 2012-09-23T16:09:35Z | [
"python",
"gevent"
] | For debugging purposes, I would like to iterate over all greenlets and obtain their trace traces -- how can I do that with gevent?
Basically, I would like to do the gevent equivalent of [this](http://stackoverflow.com/questions/1032813/dump-stacktraces-of-all-active-threads). | You can use the `gc` module to iterate through all the objects on the heap and search for greenlets. Greenlets store the stack traces as an attribute `gr_frame`.
```
import gc
import traceback
from greenlet import greenlet
for ob in gc.get_objects():
if not isinstance(ob, greenlet):
continue
if not ob... |
How to decode an invalid json string in python | 12,511,159 | 4 | 2012-09-20T10:54:13Z | 12,511,364 | 7 | 2012-09-20T11:07:26Z | [
"python",
"json",
"python-2.7"
] | I wonder if there is a way to decode a JSON-like string.
I got string:
```
'{ hotel: { id: "123", name: "hotel_name"} }'
```
It's not a valid JSON string, so I can't decode it directly with the python API.
Python will only accept a stringified JSON string like:
```
'{ "hotel": { "id": "123", "name": "hotel_name"} ... | Use [demjson](http://deron.meranda.us/python/demjson/) module, which has ability to decode in non-strict mode.
```
In [1]: import demjson
In [2]: demjson.decode('{ hotel: { id: "123", name: "hotel_name"} }')
Out[2]: {u'hotel': {u'id': u'123', u'name': u'hotel_name'}}
``` |
Hooking into sqlalchemy models | 12,512,662 | 2 | 2012-09-20T12:34:17Z | 12,513,904 | 9 | 2012-09-20T13:39:50Z | [
"python",
"orm",
"sqlalchemy",
"hook"
] | I'm looking to hook into the model creation cycle for sqlalchemy models. For example on create or on save (like in the Ruby ORM ActiveRecord, in fact I'm moving a model from ActiveRecord to SqlAlchemy).
Events looks like what I need: <http://docs.sqlalchemy.org/en/rel_0_7/core/event.html>, but I haven't found more det... | Events are pretty simple once you get the hang of it.
Here is a quick example using events
```
import uuid
from sqlalchemy.event import listen
from mypackage.models import Base
def generate_license(mapper, connect, target):
target.generate_license()
class User(Base):
__tablename__ = "users"
id = C... |
Hooking into sqlalchemy models | 12,512,662 | 2 | 2012-09-20T12:34:17Z | 26,611,082 | 8 | 2014-10-28T14:37:01Z | [
"python",
"orm",
"sqlalchemy",
"hook"
] | I'm looking to hook into the model creation cycle for sqlalchemy models. For example on create or on save (like in the Ruby ORM ActiveRecord, in fact I'm moving a model from ActiveRecord to SqlAlchemy).
Events looks like what I need: <http://docs.sqlalchemy.org/en/rel_0_7/core/event.html>, but I haven't found more det... | ```
from sqlalchemy.event import listen_for
â¦
class User(Base):
â¦
@listen_for(User, 'before_insert')
@staticmethod
def generate_license(mapper, connect, self):
â¦
```
This will return
```
NameError: name 'User' is not defined
``` |
reading file with missing values in python pandas | 12,514,590 | 5 | 2012-09-20T14:16:45Z | 12,514,711 | 9 | 2012-09-20T14:22:29Z | [
"python",
"pandas"
] | I try to read .txt with missing values using pandas.read\_csv. My data is of the format:
```
10/08/2012,12:10:10,name1,0.81,4.02,50;18.5701400N,4;07.7693770E,7.92,10.50,0.0106,4.30,0.0301
10/08/2012,12:10:11,name2,,,,,10.87,1.40,0.0099,9.70,0.0686
```
with thousands of samples with same name of the point, gps positio... | The parameter `na_values` must be "list like" (see this [answer](http://stackoverflow.com/a/9941582/1240268)).
A string is "list like" so:
```
na_values='abc' # would transform the letters 'a', 'b' and 'c' each into `nan`
# is equivalent to
na_values=['a','b','c']`
```
Similarly:
```
na_values=''
# is equivalent to... |
assertRaises fails, even the callable raises the required exception (python, unitest) | 12,516,881 | 7 | 2012-09-20T16:27:34Z | 12,516,955 | 7 | 2012-09-20T16:31:38Z | [
"python",
"unit-testing"
] | I have the following test-code checking for an exception raising in a function. I expect the test to pass, but a failure is indicated instead. Here is the test code:
```
import unittest
# define a user-defined exception
class MyException(Exception):
def __str__(self):
return repr("ERROR: Just raised my ex... | Due to the rules of the languages, the arguments are evaluated before the code of the called function is entered (and that's generally a good thing). Therefore, `assertRaises` can't catch exceptions occuring during evaluation of arguments. The workaround (in more than one API) is that you *pass a callable* to methods l... |
assertRaises fails, even the callable raises the required exception (python, unitest) | 12,516,881 | 7 | 2012-09-20T16:27:34Z | 12,516,956 | 13 | 2012-09-20T16:31:40Z | [
"python",
"unit-testing"
] | I have the following test-code checking for an exception raising in a function. I expect the test to pass, but a failure is indicated instead. Here is the test code:
```
import unittest
# define a user-defined exception
class MyException(Exception):
def __str__(self):
return repr("ERROR: Just raised my ex... | `assertRaises` calls the function for you. By calling it yourself, the exception is raised *before* `assertRaises` can test it.
Change your code to:
```
self.assertRaises(MyException, other.func)
```
and it'll work correctly. Alternatively, you can use `assertRaises` as a context manager (python 2.7 and up):
```
wi... |
sqlalchemy conditional multiple filters on dynamic lazy relationship | 12,517,414 | 5 | 2012-09-20T17:04:34Z | 12,517,683 | 9 | 2012-09-20T17:23:44Z | [
"python",
"sqlalchemy",
"flask",
"flask-sqlalchemy"
] | I am using sqlalchemy with the following models
```
class Page(db.Model):
id= ..
posts = db.relationship('Post', lazy='dynamic')
class Post(db.Model):
id=..
page_id=..
author= db.Column(db.String)
date= db.Column(db.DateTime)
```
in the Page class I have a method to get the page's posts for a s... | `filter()` returns a new query object, but you do not store it. Replace `p` with the result each time:
```
if start_date:
p = p.filter(Post.date >= start_date)
if end_date:
p = p.filter(Post.date <= end_date)
return p
``` |
PyCharm autocomplete | 12,517,535 | 9 | 2012-09-20T17:11:59Z | 12,518,290 | 10 | 2012-09-20T18:05:04Z | [
"python",
"autocomplete",
"pycharm"
] | I'm completely new to Python and PyCharm and I cannot figure out why PyCharm doesn't auto-completes very simple cases such as:
```
import pickle
pickle.dum[control+space or control+shift+space results nothing here]
```
I have PyCharm 2.6.2 and Python 2.7.1. What's wrong?
**Add:**
I'm on Mac OS 10.7.3 | Can't reproduce. Make sure you have a valid Python interpreter configured for the project. Also try `File` | `Invalidate Caches`.
 |
Double underscore for Python method *argument* | 12,517,877 | 10 | 2012-09-20T17:38:18Z | 12,517,966 | 11 | 2012-09-20T17:43:59Z | [
"python"
] | I know what double underscore means for Python class attributes/methods, but does it mean something for method argument?
It looks like you cannot pass argument starting with double underscore to methods. It is confusing because you can do that for normal functions.
Consider this script:
```
def egg(__a=None):
re... | Name mangling applies to all identifiers with leading double underscores, [regardless of where they occur](http://docs.python.org/reference/expressions.html#atom-identifiers) (second to last sentence in that section):
> This transformation is independent of the syntactical context in which the identifier is used.
Thi... |
Numpy Indexing: Return the rest | 12,518,043 | 7 | 2012-09-20T17:48:50Z | 12,518,492 | 7 | 2012-09-20T18:17:28Z | [
"python",
"arrays",
"numpy",
"indexing",
"scipy"
] | A simply example of numpy indexing:
```
In: a = numpy.arange(10)
In: sel_id = numpy.arange(5)
In: a[sel_id]
Out: array([0,1,2,3,4])
```
How do I return the rest of the array that are not indexed by sel\_id? What I can think of is:
```
In: numpy.array([x for x in a if x not in a[id]])
out: array([5,6,7,8,9])
```
Is ... | For this simple 1D case, I'd actually use a boolean mask:
```
a = numpy.arange(10)
include_index = numpy.arange(4)
include_idx = set(include_index) #Set is more efficient, but doesn't reorder your elements if that is desireable
mask = numpy.array([(i in include_idx) for i in xrange(len(a))])
```
Now you can get your... |
pip ignores dependency_links in setup.py | 12,518,499 | 18 | 2012-09-20T18:17:42Z | 13,587,734 | 32 | 2012-11-27T15:40:20Z | [
"python",
"pip",
"setuptools",
"distutils",
"easy-install"
] | I have dependency\_links in my setup.py:
```
...
dependency_links = ['http://github.com/robot-republic/python-s3/tarball/master.tar.gz#egg=python-s3'],
...
```
But it doesn't work. However install\_requires works fine.
Maybe there are another method to set up git repo as required for setup.py? | [This answer](http://stackoverflow.com/questions/3472430/how-can-i-make-setuptools-install-a-package-thats-not-on-pypi) should help. In a nutshell, you need to specify the version (or "dev") for the `#egg=python-s3` so it looks like `#egg=python-s3-1.0.0`.
Updates based on @Cerin's comment:
* Pip 1.5.x has a flag to ... |
scrape websites with infinite scrolling | 12,519,074 | 19 | 2012-09-20T18:56:22Z | 12,519,990 | 16 | 2012-09-20T19:57:52Z | [
"python",
"screen-scraping",
"scraper"
] | I have written many scrapers but I am not really sure how to handle infinite scrollers. These days most website etc, Facebook, Pinterest has infinite scrollers. | Most sites that have infinite scrolling do (as Lattyware notes) have a proper API as well, and you will likely be better served by using this rather than scraping.
But if you must scrape...
Such sites are using JavaScript to request additional content from the site when you reach the bottom of the page. All you need ... |
scrape websites with infinite scrolling | 12,519,074 | 19 | 2012-09-20T18:56:22Z | 26,814,351 | 18 | 2014-11-08T06:07:44Z | [
"python",
"screen-scraping",
"scraper"
] | I have written many scrapers but I am not really sure how to handle infinite scrollers. These days most website etc, Facebook, Pinterest has infinite scrollers. | You can use selenium to scrap the infinite scrolling website like twitter or facebook.
Step 1 : Install Selenium using pip
```
pip install selenium
```
Step 2 : use the code below to automate infinite scroll and extract the source code
```
from selenium import webdriver
from selenium.webdriver.common.by import By
f... |
Python3: Invalid Syntax | 12,519,554 | 6 | 2012-09-20T19:26:21Z | 12,519,594 | 11 | 2012-09-20T19:28:50Z | [
"python",
"python-3.x"
] | I am a beginner in Python and have been testing different kinds of sample code. When I started using Python3 instead of 2.7; I came upon a syntax error, but I don't understand how to fix that error.
```
File "app.py", line 101
except InvalidUserPass, e:
^
SyntaxError: invalid syntax
```... | Change
```
except InvalidUserPass, e:
```
to
```
except InvalidUserPass as e:
```
See [this](http://docs.python.org/tutorial/errors.html) for more info. |
Recursive change-making algorithm | 12,520,263 | 6 | 2012-09-20T20:17:07Z | 12,520,459 | 12 | 2012-09-20T20:29:56Z | [
"python",
"algorithm",
"recursion",
"dynamic-programming",
"coin-change"
] | Given a target amount and a list of coin denominations, my code is supposed to find the fewest coins needed to reach the target amount.
Examples:
* `C(48, [1, 5, 10, 25, 50]) = 6`
+ we can make 48 from 3x`25` + 3x`1`, so 6 coins are required
* `C(48, [1, 7, 24, 42]) = 2`
+ 48 = 2x`24`, so 2 coins are sufficient... | It's the [change-making](https://en.wikipedia.org/wiki/Change-making_problem) problem. Here's the standard recursive solution, `V` is the list of coins and `C` the target amount of money:
```
def min_change(V, C):
def min_coins(i, aC):
if aC == 0:
return 0
elif i == -1 or aC < 0:
... |
Installing PIP packages to a Virtualenv using a download cache | 12,521,552 | 9 | 2012-09-20T22:00:55Z | 12,525,243 | 18 | 2012-09-21T06:21:09Z | [
"python",
"django",
"pip",
"pypi"
] | What's the proper way to install pip packages to a virtualenv using cached packages? I've tried setting `--timeout=360` and `--use-mirrors`, but pypi performance is so flakey, it routinely hangs or disconnects, making deployments a crapshoot.
So, my plan was to use the --download-cache option to pre-download all packa... | The problem seems to be that `--download-cache` can only be used to specify the cache for downloading, not for installing. Therefore `pip` is still looking at `/usr/local/myapp/.env/build/Django` instead of `/usr/local/pip/cache`. Have you tried moving
```
pip install --upgrade --timeout=120 --use-mirrors --no-install... |
usage of __init__.py | 12,521,839 | 5 | 2012-09-20T22:29:45Z | 12,521,941 | 11 | 2012-09-20T22:39:12Z | [
"python"
] | I use `__init__.py` to run checks when I do `from myprojects.something import blabla`.
Today I started using `pyzmq` and I wanted to see what's going on behind the scenes. So I browsed the code in github and I find (for me) some strange usage of `__init__.py` there that I cannot explain myself.
For example [`zmq/core... | The `__all__` is for when someone does `from module import *` as documented [here](http://docs.python.org/tutorial/modules.html?highlight=__all__#importing-from-a-package).
> The only solution is for the package author to provide an explicit
> index of the package. The import statement uses the following
> convention:... |
How can I tail a log file in Python? | 12,523,044 | 36 | 2012-09-21T01:13:58Z | 12,523,119 | 21 | 2012-09-21T01:25:39Z | [
"python",
"tail"
] | I'd like to make the output of tail -F or something similar available to me in Python without blocking or locking. I've found some really old code to do that [here](http://code.activestate.com/recipes/436477-filetailpy/), but I'm thinking there must be a better way or a library to do the same thing by now. Anyone know ... | Using the [sh module](http://amoffat.github.io/sh/) (pip install sh):
```
from sh import tail
# runs forever
for line in tail("-f", "/var/log/some_log_file.log", _iter=True):
print(line)
```
[update]
Since sh.tail with `_iter`=True is a generator, you can:
```
import sh
tail = sh.tail("-f", "/var/log/some_log_f... |
How can I tail a log file in Python? | 12,523,044 | 36 | 2012-09-21T01:13:58Z | 12,523,302 | 20 | 2012-09-21T01:59:54Z | [
"python",
"tail"
] | I'd like to make the output of tail -F or something similar available to me in Python without blocking or locking. I've found some really old code to do that [here](http://code.activestate.com/recipes/436477-filetailpy/), but I'm thinking there must be a better way or a library to do the same thing by now. Anyone know ... | The only *portable* way to `tail -f` a file appears to be, in fact, to read from it and retry (after a `sleep`) if the `read` returns 0. The `tail` utilities on various platforms use platform-specific tricks (e.g. `kqueue` on BSD) to efficiently tail a file forever without needing `sleep`.
Therefore, implementing a go... |
How can I tail a log file in Python? | 12,523,044 | 36 | 2012-09-21T01:13:58Z | 12,523,371 | 32 | 2012-09-21T02:09:27Z | [
"python",
"tail"
] | I'd like to make the output of tail -F or something similar available to me in Python without blocking or locking. I've found some really old code to do that [here](http://code.activestate.com/recipes/436477-filetailpy/), but I'm thinking there must be a better way or a library to do the same thing by now. Anyone know ... | ## Non Blocking
If you are on linux (as windows does not support calling select on files) you can use the subprocess module along with the select module.
```
import time
import subprocess
import select
f = subprocess.Popen(['tail','-F',filename],\
stdout=subprocess.PIPE,stderr=subprocess.PIPE)
p = select.pol... |
f2py: Specifying real precision in fortran when interfacing with python? | 12,523,524 | 5 | 2012-09-21T02:35:54Z | 12,524,403 | 10 | 2012-09-21T04:46:45Z | [
"python",
"fortran90",
"f2py"
] | I am playing around with f2py. I'm a bit confused about numpy intrinsic types vs. fortran 90 types. It seems like I can only use single precision reals in fortran 90, when interacting with python. Let me illustrate with an example:
Say I have this fortran 90 module, test.f90, to be compiled with f2py and imported in p... | In your first example, I don't know why you say it seems like f2py doesn't accept double precision, when `test.test.r_dp` *is* double precision. A numpy array that shows a value with a decimal point and no explicit dtype is a double precision array.
The second example shows a limitation in F2PY's handling of type defi... |
getting value of the maximum key in dictionary (python) | 12,523,876 | 2 | 2012-09-21T03:34:22Z | 12,523,886 | 10 | 2012-09-21T03:35:45Z | [
"python",
"dictionary"
] | I only found here how can I get the key of the maximum value:
```
max(d, key=d.get())
```
but I need to search the maximum key and return the value of this key.
thanks, | To get the maximum key
```
max(d)
```
And for the value, just look it up in the dictionary
```
d[max(d)]
```
Note: You can also use `max(d.keys())`, but it a bit slower because it needs to build a temporary list
```
$ python -m timeit -s 'd={x:str(x) for x in range(10000)}' 'max(d)'
1000 loops, best of 3: 377 usec... |
How do you implement "#ifdef" in python? | 12,524,570 | 15 | 2012-09-21T05:08:08Z | 12,524,872 | 16 | 2012-09-21T05:42:53Z | [
"python",
"preprocessor"
] | Programming in `C` I used to have code sections only used for debugging purposes (logging commands and the like). Those statements could be completely disabled for production by using `#ifdef` pre-processor directives, like this:
```
#ifdef MACRO
controlled text
#endif /* MACRO */
```
What is the best way to do ... | If you just want to disable logging methods, use the `logging` module. If the log level is set to exclude, say, debug statements, then `logging.debug` will be very close to a no-op (it just checks the log level and returns without interpolating the log string).
If you want to actually remove chunks of code at bytecode... |
Encrypt & Decrypt using PyCrypto AES 256 | 12,524,994 | 73 | 2012-09-21T05:54:41Z | 12,525,124 | 8 | 2012-09-21T06:08:30Z | [
"python",
"encryption",
"padding",
"pycrypto",
"initialization-vector"
] | I'm trying to build two functions using PyCrypto that accept two parameters: the message and the key, and then encrypt/decrypt the message.
I found several links on the web to help me out, but each one of them has flaws:
[This one at codekoala](http://www.codekoala.com/blog/2009/aes-encryption-python-using-pycrypto/)... | You can get a passphrase out of an arbitrary password by using a cryptographic hash function (*NOT* Python's builtin `hash`) like SHA-1 or SHA-256. Python includes support for both in its standard library:
```
import hashlib
hashlib.sha1("this is my awesome password").digest() # => a 20 byte string
hashlib.sha256("an... |
Encrypt & Decrypt using PyCrypto AES 256 | 12,524,994 | 73 | 2012-09-21T05:54:41Z | 12,525,165 | 105 | 2012-09-21T06:12:54Z | [
"python",
"encryption",
"padding",
"pycrypto",
"initialization-vector"
] | I'm trying to build two functions using PyCrypto that accept two parameters: the message and the key, and then encrypt/decrypt the message.
I found several links on the web to help me out, but each one of them has flaws:
[This one at codekoala](http://www.codekoala.com/blog/2009/aes-encryption-python-using-pycrypto/)... | You may need the following two functions to pad(when do encryption) and unpad(when do decryption) when the length of input is not a multiple of BLOCK\_SIZE.
```
BS = 16
pad = lambda s: s + (BS - len(s) % BS) * chr(BS - len(s) % BS)
unpad = lambda s : s[:-ord(s[len(s)-1:])]
```
So you're asking the length of key? You... |
Encrypt & Decrypt using PyCrypto AES 256 | 12,524,994 | 73 | 2012-09-21T05:54:41Z | 21,928,790 | 42 | 2014-02-21T08:10:37Z | [
"python",
"encryption",
"padding",
"pycrypto",
"initialization-vector"
] | I'm trying to build two functions using PyCrypto that accept two parameters: the message and the key, and then encrypt/decrypt the message.
I found several links on the web to help me out, but each one of them has flaws:
[This one at codekoala](http://www.codekoala.com/blog/2009/aes-encryption-python-using-pycrypto/)... | Here is my implementation and works for me with some fixes and enhances the alignment of the key and secret phrase with 32 bytes and iv to 16 bytes:
```
import base64
import hashlib
from Crypto import Random
from Crypto.Cipher import AES
class AESCipher(object):
def __init__(self, key):
self.bs = 32
... |
Normalize data in pandas | 12,525,722 | 29 | 2012-09-21T07:04:23Z | 12,525,836 | 69 | 2012-09-21T07:14:15Z | [
"python",
"pandas",
"numpy"
] | Suppose I have a pandas data frame df:
I want to calculate the column wise mean of a data frame,
This is easy:
```
df.apply(average)
```
then the column wise range max(col) - min (col). this is easy again:
```
df.apply(max) - df.apply(min)
```
Now for each element I want to subtract its columns mean and divide by... | ```
In [92]: df
Out[92]:
a b c d
A -0.488816 0.863769 4.325608 -4.721202
B -11.937097 2.993993 -12.916784 -1.086236
C -5.569493 4.672679 -2.168464 -9.315900
D 8.892368 0.932785 4.535396 0.598124
In [93]: df_norm = (df - df.mean()) / (df.max() - df.min())
In [94]: df_n... |
Normalize data in pandas | 12,525,722 | 29 | 2012-09-21T07:04:23Z | 33,250,288 | 11 | 2015-10-21T03:10:46Z | [
"python",
"pandas",
"numpy"
] | Suppose I have a pandas data frame df:
I want to calculate the column wise mean of a data frame,
This is easy:
```
df.apply(average)
```
then the column wise range max(col) - min (col). this is easy again:
```
df.apply(max) - df.apply(min)
```
Now for each element I want to subtract its columns mean and divide by... | You can use `apply` for this, and it's a bit neater:
```
import numpy as np
import pandas as pd
np.random.seed(1)
df = pd.DataFrame(np.random.randn(4,4)* 4 + 3)
0 1 2 3
0 9.497381 0.552974 0.887313 -1.291874
1 6.461631 -6.206155 9.979247 -0.044828
2 4.276156 2.002518 8.8484... |
Callback for celery apply_async | 12,526,606 | 6 | 2012-09-21T08:09:48Z | 13,494,345 | 21 | 2012-11-21T13:27:27Z | [
"python",
"celery"
] | I use `celery` in my application to run periodic tasks. Let's see simple example below
```
from myqueue import Queue
@perodic_task(run_every=timedelta(minutes=1))
def process_queue():
queue = Queue()
uid, questions = queue.pop()
if uid is None:
return
job = group(do_stuff(q) for q in questions... | Subclass the Task class and overload the on\_success and on\_failure functions:
```
class CallbackTask(Task):
def on_success(self, retval, task_id, args, kwargs):
pass
def on_failure(self, exc, task_id, args, kwargs, einfo):
pass
@celery.task(base=CallbackTask) # this does the trick
def add... |
Custom directives in Sphinx | 12,527,783 | 12 | 2012-09-21T09:26:47Z | 12,836,645 | 9 | 2012-10-11T09:41:55Z | [
"python",
"documentation",
"python-sphinx",
"restructuredtext"
] | I'm currently documenting a rest API written in Python. All the project's documentation is created using Sphinx, for the REST API I would like to create some special directvies. For instance, let's say I have this resource defined:
```
@resource("/user/<email>", method="GET")
def user_details (email):
""" Returns ... | Sphinx can be extended with custom directives via "[Sphinx Extensions](http://sphinx.pocoo.org/extensions.html)". That is, you will need to implement a Sphinx extension providing the `query_param` custom directive, and add this extension to your Sphinx project.
Sphinx documentation provides [a tutorial](http://sphinx-... |
Passing the '+' character in a POST request in Python | 12,527,959 | 5 | 2012-09-21T09:37:36Z | 12,528,097 | 7 | 2012-09-21T09:45:15Z | [
"python",
"python-requests"
] | I am trying to do some automation in a Python script and I have run into a problem. I am trying to do a POST to a server.
```
url = 'http://www.example.com'
params = {'arg0': 'value', 'arg1': '+value'}
f = urllib.urlopen(url, urllib.urlencode(params))
print f.read()
```
I have done a wireshark capture of the equival... | The `+` character is the proper encoding for a space when quoting GET or POST data. Thus, a literal `+` character needs to be escaped as well, lest it be decoded to a space on the other end. See RFC 2396, [section 2.2](https://tools.ietf.org/html/rfc2396#section-2.2), [section 3.4](https://tools.ietf.org/html/rfc2396#s... |
how to "add" things together python | 12,530,686 | 2 | 2012-09-21T12:31:01Z | 12,530,741 | 10 | 2012-09-21T12:35:33Z | [
"python"
] | I wrote a function like this, the `op` gives a operation sign which like `'+','-','*','/'` or more, the code "adds" everything use the given operator,
**Here is the code:**
```
def arithmetic(op,*args):
result = args[0]
for x in args[1:]:
if op =='+':
result += x
elif op == '-':
... | You can use the corresponding [operators](http://docs.python.org/library/operator.html):
```
import operator
def arithmetic(opname, *args):
op = {'+': operator.add,
'-': operator.sub,
'*': operator.mul,
'/': operator.div}[opname]
result = args[0]
for x in args[1:]:
resu... |
How to make this python script fast? (benchmarking related to branch prediction from a post from here) | 12,530,812 | 4 | 2012-09-21T12:41:21Z | 24,399,639 | 7 | 2014-06-25T03:20:22Z | [
"python",
"optimization",
"branch-prediction"
] | From [here - a branching prediction problem](http://stackoverflow.com/questions/11227809/why-is-processing-a-sorted-array-faster-than-an-unsorted-array), I started to write the Python version of the program to check the runtime of the sorted/unsorted versions in Python.
I tried sorted first.
Here's the code:
```
impo... | I started with the answer by @mgilson and reworked it a bit. I wanted to test the "decision bit" and lookup table techniques as discussed in my answer to the original question: <http://stackoverflow.com/a/17782979/166949>
I made a few changes to the original. Some were just style things that reflect my personal prefer... |
String split on new line, tab and some number of spaces | 12,533,955 | 20 | 2012-09-21T15:54:34Z | 12,533,983 | 44 | 2012-09-21T15:56:07Z | [
"python",
"regex",
"split"
] | I'm trying to perform a string split on a set of somewhat irregular data that looks something like:
```
\n\tName: John Smith
\n\t Home: Anytown USA
\n\t Phone: 555-555-555
\n\t Other Home: Somewhere Else
\n\t Notes: Other data
\n\tName: Jane Smith
\n\t Misc: Data with spaces
```
I'd like to convert this into a ... | Just use [.strip()](http://docs.python.org/library/stdtypes.html#str.strip), it removes all whitespace for you, including tabs and newlines, while splitting. The splitting itself can then be done with [`data_string.splitlines()`](http://docs.python.org/library/stdtypes.html#str.splitlines):
```
[s.strip() for s in dat... |
Memory Usage in Python: What's the difference between memory_profiler and guppy? | 12,534,794 | 4 | 2012-09-21T16:53:46Z | 12,535,427 | 7 | 2012-09-21T17:36:44Z | [
"python",
"memory-profiling"
] | I'm thoroughly confused about the memory usage of a specific python script. I guess I don't really know how to profile the usage despite [advice](http://stackoverflow.com/questions/110259/python-memory-profiler) from several SO Questions/[Answers](http://stackoverflow.com/a/552810/717357).
My questions are: **What's t... | > What's the difference between memory\_profiler and guppy.hpy?
Do you understand the difference between your internal view of the heap and the OS's external view of your program? (For example, when the Python interpreter calls `free` on 1MB, that doesn't immediatelyâor maybe even everâreturn 1MB worth of pages to... |
Why is slice assignment faster than `list.insert`? | 12,537,716 | 18 | 2012-09-21T20:26:10Z | 12,537,894 | 12 | 2012-09-21T20:42:05Z | [
"python",
"performance",
"optimization",
"python-internals"
] | Inspired by [this nice answer](http://stackoverflow.com/a/12537489/748858),
Here's a benchmark:
```
import timeit
def test1():
a = [1,2,3]
a.insert(0,1)
def test2():
a = [1,2,3]
a[0:0]=[1]
print (timeit.timeit('test1()','from __main__ import test1'))
print (timeit.timeit('test2()','from __main__ im... | Your first test case has to call the method `insert` on the list `a`, whereas all the operations in `test2` are handled directly in byte code. Note the `CALL_FUNCTION` in the disassembly of `test1` below. Calling functions is moderately expensive in Python: certainly expensive enough to account for a few percent differ... |
Python "private" name mangling and instance vs class attributes | 12,537,904 | 6 | 2012-09-21T20:42:43Z | 12,537,917 | 9 | 2012-09-21T20:44:12Z | [
"python",
"attributes",
"private-members",
"name-mangling",
"underscores"
] | I was writing a decorator that needs to access private variables and found this discrepancy. Can anyone explain this?
(Python 2.5)
Naming mangling works as expected for attributes defined in the class:
```
>>> class Tester(object):
... __foo = "hi"
>>> t = Tester()
>>> t._Tester__foo
'hi'
```
Instance attribute... | That is actually *not* correct.
Name mangling takes place at class creation time; any functions that refer to mangled names are adjusted as well.
I cannot reproduce your example, at least not in Python versions 2.4, 2.5, 2.6, 3.1 and 3.2 on the Mac:
```
>>> class Tester(object):
... def __init__(self):
... ... |
Python module "cx_Oracle" module could not be found | 12,538,238 | 8 | 2012-09-21T21:13:35Z | 19,552,263 | 8 | 2013-10-23T21:05:21Z | [
"python",
"oracle",
"module",
"cx-oracle"
] | I recently installed cx\_Oracle module on my machine, in order to connect to a remote Oracle database server. (I have no Oracle client at my side).
* Python: Version 2.7 x86
* Oracle: Verision 11.1.X x64
* Cx\_Oracle:Verion-5.1.2-11g.win32-py2.7
Then everytime I run my script, it fails and print the following message... | ```
# - This import requires appropriate oraocciXX.dll to be available in PATH (on windows)
# (Probably LD_LIBRARY_PATH or LD_LIBRARY_PATH64 on POSIX)
# where XX is the oracle DB version, e.g. oraocci11.dll for Oracle 11g.
# - This dll is part of the Oracle Instant client pkg available here:
# http://www.orac... |
How do I find the longest string in Python? | 12,538,586 | 8 | 2012-09-21T21:45:21Z | 12,538,604 | 33 | 2012-09-21T21:47:16Z | [
"python",
"string",
"string-length"
] | Something like `max(len(s1), len(s2))` will only return the maximum length. But if I actually want to find out which string is longer, and perhaps save it to another string, how is that done? `max(s1,s2)` seems to return the string with the larger value, but not necessarily the longest.
Note: this has to be done witho... | `max` takes a `key` function which causes `max` to take the max `key(val)` for each `val`, yet still return the `val`, to wit:
```
>>> max("foobar", "angstalot")
'foobar'
>>> max("foobar", "angstalot", key=len)
'angstalot'
``` |
What does the underscore represent in Python? | 12,539,245 | 5 | 2012-09-21T23:09:06Z | 12,539,279 | 10 | 2012-09-21T23:13:45Z | [
"python"
] | I am kind of new to Python, so I am trying to read over existing code. I am a little confused on the syntax of this though.
For example:
```
rlist, _, _ = select.select(sockets, [], [])
```
I understand that `select.select()` takes 3 lists (and I assume `[]` just means empty list), but is the `_` used to denote a pl... | It's just the name of a variable! Usually people use `_` for variables that are temporary or insignificant.
As other people have stated, `_` is a common alias for gettext, a translation library. You can identify when it's being used as gettext if you see it called as a function, eg. `_('Hello, world!')`.
**Protip:** ... |
How to organize multiple python files into a single module without it behaving like a package? | 12,540,290 | 16 | 2012-09-22T02:51:12Z | 12,540,337 | 10 | 2012-09-22T03:02:00Z | [
"python",
"module",
"package"
] | Is there a way to use `__init__.py` to organize multiple files into a **module**?
Reason: Modules are easier to use than packages, because they don't have as many layers of namespace.
Normally it makes a package, this I get. Problem is with a package, 'import thepackage' gives me an empty namespace. Users must then e... | You can sort of do it, but it's not really a good idea and you're fighting against the way Python modules/packages are supposed to work. By importing appropriate names in `__init__.py` you can make them accessible in the package namespace. By deleting module names you can make them inaccessible. (For why you need to de... |
Test if an index of a list exists | 12,540,600 | 4 | 2012-09-22T04:07:21Z | 12,540,662 | 7 | 2012-09-22T04:18:44Z | [
"python"
] | Okay, so this is actually two questions. First, I want to know if there is a way to test if an index of a list exists. For example, I want to increment list[i] each time a given condition is true using code like `list[i] += 1`, but if the index doesn't exists, I'm given an error. So I want to set up a test that, in the... | Test if an index exists:
```
if 0 <= i < len(list): ... do something with list[i] ...
else: ... i is out of bounds, do something else ...
```
In this situation, you're probably better off using a [`dict`](http://docs.python.org/library/stdtypes.html#dict) instead of an array, and possibly a [`defaultdict`](http://doc... |
Test if an index of a list exists | 12,540,600 | 4 | 2012-09-22T04:07:21Z | 12,540,663 | 8 | 2012-09-22T04:18:59Z | [
"python"
] | Okay, so this is actually two questions. First, I want to know if there is a way to test if an index of a list exists. For example, I want to increment list[i] each time a given condition is true using code like `list[i] += 1`, but if the index doesn't exists, I'm given an error. So I want to set up a test that, in the... | It sounds like what you really want is a `defaultdict` -- not a list so much as a mapping of integers to some sort of count of the number of times you've seen them.
(this is really close to the concept of autovivificaiton in perl, if you've used that before)
This code would work:
```
from collections import defaultd... |
How to get Excel cell properties in Python | 12,540,856 | 4 | 2012-09-22T05:01:31Z | 12,541,180 | 9 | 2012-09-22T06:03:18Z | [
"python",
"xlrd"
] | Actually I am using xlrd module 0.8 version, but I don't know how to read cell properties like background color, font, and whether cell is locked.
I tried to use
```
import xlrd
wb = xlrd.open_workbook(...)
sh = wb.sheet_by_index(...)
sh.sh._cell_xf_indexes(2, 2)
```
It raises an error saying formatting information ... | The following works for me, using xlrd version 0.7.6:
```
from xlrd import open_workbook
wb = open_workbook('tmp.xls', formatting_info=True)
sheet = wb.sheet_by_name("1")
cell = sheet.cell(6, 0)
print "cell.xf_index is", cell.xf_index
fmt = wb.xf_list[cell.xf_index]
print "type(fmt) is", type(fmt)
print
print "fmt.du... |
what is the most efficient way to turn a list in python | 12,541,074 | 3 | 2012-09-22T05:42:42Z | 12,541,099 | 10 | 2012-09-22T05:46:38Z | [
"python"
] | so I have this list in python,
```
a= [[1,2,3,4],
[2,4,5,1],
[3,4,6,2],
[2,3,4,5]]
```
and want to turn the list reading horizontally to vertically.
```
b= [[1,2,3,2],
[2,4,4,3],
[3,5,6,4],
[4,1,2,5]]
```
what is the best way to do it, and most efficient way to do it? i'm pre... | You can do it like that:
```
zip(*your_list)
```
Proof:
```
>>> a = [[1, 2, 3, 4], [2, 4, 5, 1], [3, 4, 6, 2], [2, 3, 4, 5]]
>>> zip(*a)
[(1, 2, 3, 2), (2, 4, 4, 3), (3, 5, 6, 4), (4, 1, 2, 5)]
``` |
what is the most efficient way to turn a list in python | 12,541,074 | 3 | 2012-09-22T05:42:42Z | 12,541,101 | 8 | 2012-09-22T05:47:44Z | [
"python"
] | so I have this list in python,
```
a= [[1,2,3,4],
[2,4,5,1],
[3,4,6,2],
[2,3,4,5]]
```
and want to turn the list reading horizontally to vertically.
```
b= [[1,2,3,2],
[2,4,4,3],
[3,5,6,4],
[4,1,2,5]]
```
what is the best way to do it, and most efficient way to do it? i'm pre... | Check out [numpy](http://numpy.scipy.org/) library. You can put your list into an array and transpose it like this:
```
a = array ([[1,2,3,4],
[2,4,5,1],
[3,4,6,2],
[2,3,4,5]])
a.transpose()
```
P.S.: Explanation of [Tadeck](http://stackoverflow.com/users/548696/tadeck)'s solution is very easy. `... |
Flask - nested rest api - use something other than methodview or have I made a bad design? | 12,541,129 | 5 | 2012-09-22T05:53:15Z | 12,541,130 | 7 | 2012-09-22T05:53:15Z | [
"python",
"api",
"rest",
"flask"
] | Just starting off with Flask, following along at <http://flask.pocoo.org/docs/views/>
Say I have a basic REST api, in this case for symptoms:
```
/
GET - list
POST - create
/<symptomid>
GET - detail
PUT - replace
PATCH - patch
DELETE - delete
```
I can implement this pretty cleanly with Flas... | I think the design is ok. `MethodView` should be pretty awesome for it. You can put the routes together like so:
```
class SymptomDiagnosisAPI(MethodView):
"""
/<symptom_id>/diagnoses/
GET - list diags for symptoms
POST - {id: diagid} - create relation with diagnosis
/<symptom_id>/diagnose... |
Python 3: Asterisk in print function | 12,542,544 | 13 | 2012-09-22T09:24:17Z | 12,542,649 | 13 | 2012-09-22T09:39:23Z | [
"python",
"python-3.x"
] | Let's have a look:
```
print([object, ...], *, sep=' ', end='\n', file=sys.stdout)
```
<http://docs.python.org/py3k/library/functions.html?highlight=print#print>
How can we interpret that `'*'`?
Usually an asterisk ('\*') means numerous objects. But herein it is a mystery to me. Between two commas... I'm even afraid... | It means that the following arguments are keyword-only i.e., you can't supply them as positional arguments, you must use their names e.g.:
```
>>> def f(*, a): pass
...
>>> f(1)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: f() takes exactly 0 positional arguments (1 given)
>>> f... |
Python 3: Asterisk in print function | 12,542,544 | 13 | 2012-09-22T09:24:17Z | 12,542,650 | 15 | 2012-09-22T09:39:25Z | [
"python",
"python-3.x"
] | Let's have a look:
```
print([object, ...], *, sep=' ', end='\n', file=sys.stdout)
```
<http://docs.python.org/py3k/library/functions.html?highlight=print#print>
How can we interpret that `'*'`?
Usually an asterisk ('\*') means numerous objects. But herein it is a mystery to me. Between two commas... I'm even afraid... | That's an error in the documentation, inserted by someone applying a new Python 3 feature to places where it shouldn't be used. It has since been fixed (see [issue 15831](http://bugs.python.org/issue15831)).
The function signatures in the document used is given in a psuedo-formal-grammar form, but adding in the `*` ma... |
xvfb failed to start in ubuntu | 12,542,675 | 3 | 2012-09-22T09:42:29Z | 12,793,696 | 8 | 2012-10-09T06:02:37Z | [
"python",
"qt",
"ubuntu",
"webkit",
"xvfb"
] | I trying to get a screen shot by using the following two tools (something relative to qt, webkit and etc. maybe)
* <https://github.com/adamn/python-webkit2png>
* <http://cutycapt.sourceforge.net/>
when run it on server using xvfb-run following the guide of them, I got the error: Xvfb failed to start
then I searched ... | It works when I remove "-server-args". Try doing that.
```
xvfb-run --auto-servernum --server-num=1 python webkit2png.py --url=http://google.com --out=test.png
```
This is the command you're looking for. |
Python: iterating over list vs over dict items efficiency | 12,543,837 | 5 | 2012-09-22T12:38:16Z | 12,543,887 | 15 | 2012-09-22T12:44:32Z | [
"python",
"performance",
"list",
"dictionary"
] | Is iterating over `some_dict.items()` as efficient as iterating over a list of the same items in CPython? | It depends on which version of Python you're using. In Python 2, `some_dict.items()` creates a new list, which takes up some additional time and uses up additional memory. On the other hand, once the list is created, it's a list, and so should have identical performance characteristics after the overhead of list creati... |
How to I get the current IPython Notebook name | 12,544,056 | 23 | 2012-09-22T13:09:59Z | 13,055,551 | 12 | 2012-10-24T18:35:29Z | [
"python",
"ipython"
] | I am trying to obtain the current NoteBook name when running the ipython notebook. I know I can see it at the top of the notebook. What I am after something like
```
currentNotebook = IPython.foo.bar.notebookname()
```
I need to get the name in a variable. | As already mentioned you probably aren't really supposed to be able to do this, but I did find a way. It's a flaming hack though so don't rely on this at all:
```
import json
import os
import urllib2
import IPython
from IPython.lib import kernel
connection_file_path = kernel.get_connection_file()
connection_file = os.... |
How to I get the current IPython Notebook name | 12,544,056 | 23 | 2012-09-22T13:09:59Z | 23,619,544 | 11 | 2014-05-12T21:54:21Z | [
"python",
"ipython"
] | I am trying to obtain the current NoteBook name when running the ipython notebook. I know I can see it at the top of the notebook. What I am after something like
```
currentNotebook = IPython.foo.bar.notebookname()
```
I need to get the name in a variable. | I have the following which works with IPython 2.0. I observed that the name of the notebook is stored as the value of the attribute `'data-notebook-name'` in the `<body>` tag of the page. Thus the idea is first to ask Javascript to retrieve the attribute --javascripts can be invoked from a codecell thanks to the `%%jav... |
How to I get the current IPython Notebook name | 12,544,056 | 23 | 2012-09-22T13:09:59Z | 30,942,416 | 11 | 2015-06-19T15:55:59Z | [
"python",
"ipython"
] | I am trying to obtain the current NoteBook name when running the ipython notebook. I know I can see it at the top of the notebook. What I am after something like
```
currentNotebook = IPython.foo.bar.notebookname()
```
I need to get the name in a variable. | On Jupyter 3.0 the following works. Here I'm showing the entire path on the Jupyter server, not just the notebook name:
To store the `NOTEBOOK_FULL_PATH` on the current notebook front end:
```
%%javascript
var nb = IPython.notebook;
var kernel = IPython.notebook.kernel;
var command = "NOTEBOOK_FULL_PATH = '" + nb.bas... |
Parsing apache log files | 12,544,510 | 19 | 2012-09-22T14:15:29Z | 12,544,587 | 30 | 2012-09-22T14:25:18Z | [
"python",
"file-io"
] | I just started learning Python and would like to read an Apache log file and put parts of each line into different lists.
line from the file
> 172.16.0.3 - - [25/Sep/2002:14:04:19 +0200] "GET / HTTP/1.1" 401 - "" "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.1) Gecko/20020827"
according to [Apache website](http://ht... | This is a job for [regular expressions](http://docs.python.org/howto/regex.html).
For example:
```
line = '172.16.0.3 - - [25/Sep/2002:14:04:19 +0200] "GET / HTTP/1.1" 401 - "" "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.1) Gecko/20020827"'
regex = '([(\d\.)]+) - - \[(.*?)\] "(.*?)" (\d+) - "(.*?)" "(.*?)"'
import... |
Parsing apache log files | 12,544,510 | 19 | 2012-09-22T14:15:29Z | 12,544,831 | 11 | 2012-09-22T14:54:36Z | [
"python",
"file-io"
] | I just started learning Python and would like to read an Apache log file and put parts of each line into different lists.
line from the file
> 172.16.0.3 - - [25/Sep/2002:14:04:19 +0200] "GET / HTTP/1.1" 401 - "" "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.1) Gecko/20020827"
according to [Apache website](http://ht... | Use a regular expression to split a row into separate "tokens":
```
>>> row = """172.16.0.3 - - [25/Sep/2002:14:04:19 +0200] "GET / HTTP/1.1" 401 - "" "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.1) Gecko/20020827" """
>>> import re
>>> map(''.join, re.findall(r'\"(.*?)\"|\[(.*?)\]|(\S+)', row))
['172.16.0.3', '-', '... |
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