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6,000 | class parsepage(htmlparser)def handle_starttag(selftagattrs)print('tag start:'tagattrsdef handle_endtag(selftag)print('tag end'tagdef handle_data(selfdata)print('data 'data rstrip()nowcreate web page' html text stringwe hardcode one herebut it might also be loaded from fileor fetched from website with urllib requestpag... |
6,001 | here' another html parsing examplein we used simple method exported by this module to unquote html escape sequences ( entitiesin strings embedded in an html reply pageimport cgihtml parser cgi escape(" hello" ' < < >hello</ >html parser htmlparser(unescape( ' hellothis works for undoing html escapesbut t... |
6,002 | now that you understand the basic principles of the html parser class in python' standard librarythe plain text extraction module used by ' pymailgui (example - will also probably make significantly more sense (this was an unavoidable forward reference which we're finally able to closerather than repeating its code her... |
6,003 | interfaces to such common parser generators are freely available in the open source domain (run web search for up-to-date details and linksin additiona number of python-specific parsing systems are available on the web among themply is an implementation of lex and yacc parsing tools in and for pythonthe kwparsing syste... |
6,004 | but there' growing library of available components that you can pick up for free and community of experts to query visit the pypi site at to python software resourcesor search the web at large with at least one million python users out there as write this bookmuch can be found in the prior-art department unlessof cours... |
6,005 | expr-tail -'+expr-tail -'-[end[+[-factor -[numbervariablefactor-tail -factor-tail -'*factor-tail -'/[+-end[*[/term -term -term -'(')[number[variable[(tokens()numvar-+/*setend this is fairly typical grammar for simple expression languageand it allows for arbitrary expression nesting (some example expressions appear at t... |
6,006 | and it' another example of the object-oriented programming (oopcomposition relationship at workparsers embed and delegate to scanners the module in example - implements the lexical analysis task--detecting the expression' basic tokens by scanning the text string left to right on demand notice that this is all straightf... |
6,007 | str 'while self text[ixin string digitsstr +self text[ixix + if self text[ix='str +ix + while self text[ixin string digitsstr +self text[ixix + self token 'numself value float(strelseself token 'numself value int(strsubsumes long(in elif self text[ixin string ascii_lettersstr 'while self text[ixin (string digits string... |
6,008 | reuse this parsertryself lex scan(get first token self goal(parse sentence except syntaxerrorprint('syntax error at column:'self lex startself lex showerror(except lexicalerrorprint('lexical error at column:'self lex startself lex showerror(except undefinederror as ename args[ print("'%sis undefined at column:nameself ... |
6,009 | left left self term(elseraise syntaxerror(def term(self)if self lex token ='num'val self lex match('num'return val elif self lex token ='var'if self lex value in self vars keys()val self vars[self lex valueself lex scan(return val elseraise undefinederror(self lex valueelif self lex token ='('self lex scan(val self exp... |
6,010 | both and /in our grammar)but we'll follow python ' lead here example - pp \lang\parser\testparser py ""###########################################################################parser test code ###########################################################################""def test(parserclassmsg)print(msgparserclassx pa... |
6,011 | as usualwe can also test and use the system interactively to work through more of its utilityc:\pp \lang\parserpython import parser parser parser( parse(' ' error cases are trapped and reported in fairly friendly fashion (assuming users think in zero-based terms) parse(' ''ais undefined at column = = parse(' + + ''ais ... |
6,012 | as the custom parser system demonstratesmodular program design is almost always major win by using python' program structuring tools (functionsmodulesclassesand so on)big tasks can be broken down into smallmanageable parts that can be coded and tested independently for instancethe scanner can be tested without the pars... |
6,013 | enter= enter=stop adding parse tree interpreter one weakness in the parser program is that it embeds expression evaluation logic in the parsing logicthe result is computed while the string is being parsed this makes evaluation quickbut it can also make it difficult to modify the codeespecially in larger systems to simp... |
6,014 | class binarynode(treenode)def __init__(selfleftright)inherited methods self leftself right leftright left/right branches def validate(selfdict)self left validate(dictrecurse down branches self right validate(dictdef trace(selflevel)print(level '[self label ']'self left trace(level+ self right trace(level+ class timesno... |
6,015 | print(level self namecomposites class assignnode(treenode)def __init__(selfvarval)self varself val varval def validate(selfdict)self val validate(dictdon' validate var def apply(selfdict)self var assignself val apply(dict)dict def trace(selflevel)print(level 'set 'self var trace(level self val trace(level #############... |
6,016 | self lex showerror(def interpret(selftree)result tree apply(self varsif result !noneprint(resultreturns none tree evals itself ignore 'setresult ignores errors def goal(self)if self lex token in ['num''var''(']tree self expr(self lex match('\ 'return tree elif self lex token ='set'tree self assign(self lex match('\ 're... |
6,017 | if self lex token ='num'leaf numnode(self lex match('num')return leaf elif self lex token ='var'leaf varnode(self lex valueself lex startself lex scan(return leaf elif self lex token ='('self lex scan(tree self expr(self lex match(')'return tree elseraise syntaxerror(####################################################... |
6,018 | import syntax for the latter caseand import from another directory when testing interactivelyc:\pp \lang\parserparser py parser rest is same as for parser :pp \lang\parserpython import parser from scanner import scannersyntaxerrorlexicalerror valueerrorattempted relative import in non-package from pytree :\pp \lang\par... |
6,019 | traceme true parse(' '[+ [* when this tree is evaluatedthe apply method recursively evaluates subtrees and applies root operators to their results hereis evaluated before +since it' lower in the tree the factor method consumes the substring before returning right subtree to expr the next tree takes different shapep par... |
6,020 | but wait--there is better way to explore parse tree structures figure - shows the parse tree generated for the string ( )displayed in pytreethe tree visualization gui described at the end of this works only because the parser module builds the parse tree explicitly (parser evaluates during parse insteadand because pytr... |
6,021 | tree shape produced for given expressionstart pytreeclick on its parser radio buttontype the expression in the input field at the bottom rightand press "input(or your enter keythe parser class is run to generate tree from your inputand the gui displays the result depending on the operators used within an expressionsome... |
6,022 | platforms and because it is implemented with classesit is both standalone program and reusable object library simple calculator gui before show you how to write full-blown calculatorthoughthe module shown in example - starts this discussion in simpler terms it implements limited calculator guiwhose buttons just add tex... |
6,023 | elsetext set(''excepttext set("error"bad as statement tooworked as statement other eval expression errors if __name__ ='__main__'calcgui(mainloop(figure - the calc script in action on windows (result= building the gui nowthis is about as simple as calculator can bebut it demonstrates the basics this window comes up wit... |
6,024 | row and each character in the string represents button lambdas are used to save extra callback data for each button the callback functions retain the button' character and the linked text entry variable so that the character can be added to the end of the entry widget' current string on press notice how we must pass in... |
6,025 | parsesevaluatesand returns the result of python expression represented as string exec runs an arbitrary python statement represented as stringand has no return value both accept optional dictionaries to be used as global and local namespaces for assigning and evaluating names used in the code strings in the calculators... |
6,026 | it can also be embedded in container class--example - attaches the simple calculator' widget packagealong with extrasto common parent example - pp \lang\calculator\calc emb py from tkinter import from calc import calcgui add parentno master calls class outerdef __init__(selfparent)embed gui label(parenttext='calc attac... |
6,027 | of coursereal calculators don' usually work by building up expression strings and evaluating them all at oncethat approach is really little more than glorified python command line traditionallyexpressions are evaluated in piecemeal fashion as they are enteredand temporary results are displayed as soon as they are compu... |
6,028 | if you do run thisyou'll notice that pycalc implements normal calculator model-expressions are evaluated as enterednot all at once at the end that isparts of an expression are computed and displayed as soon as operator precedence and manually typed parentheses allow the result in figure - for instancereflects pressing ... |
6,029 | dictionary is thrown up in the main window for use in larger expressions you can use this as an escape mechanism to employ external tools in your calculations for instanceyou can import and use functions coded in python or within these pop ups the current value in the main calculator window is stored in newly opened co... |
6,030 | evaluator class the evaluator class manages two stacks one stack records pending operators ( +)and one records pending operands ( temporary results are computed as new operators are sent from calcgui and pushed onto the operands stack as you can see from thisthe magic of expression evaluation boils down to juggling the... |
6,031 | is pushed onto operandsand the final on operators is applied to stacked operands the text input and display field at the top of the gui' main window plays part in this algorithmtoo the text input field and expression stacks are integrated by the calculator class in generalthe text input field always holds the prior ope... |
6,032 | is displayed in the entry field on pressing "eval,the rest is evaluated (( )( + ))and the final result ( is shown this result in the entry field itself becomes the left operand of future operator entered keys" [result (['+''*''(''+''*'][' '' '' '' '' '](['+''*''(''+'][' '' '' '' '](['+''*'][' '' '' '](['+'][' '' '][on ... |
6,033 | applied by calling eval when an error occurs inside an expressiona result operand of *erroris pushedwhich makes all remaining operators fail in eval too *erroressentially percolates to the top of the expression at the endit' the last operand and is displayed in the text entry field to alert you of the mistake entered k... |
6,034 | -use justify=right for input field so it displays on rightnot left-add ' +and ' -buttons (and 'ekeypressfor float exponents'ekeypress must generally be followed digitsnot or optr key-remove 'lbutton (but still allow 'lkeypress)superfluous nowbecause python auto converts up if too big ('lforced this in past)-use smaller... |
6,035 | fontcolor configurable self entry config(font=font make display larger self entry config(justify=right on rightnot left for row in self operandsfrm frame(selftopfor char in rowbutton(frmleftcharlambda op=charself onoperand(op)fg=fgbg=bgfont=fontfrm frame(selftopfor char in self operatorsbutton(frmleftcharlambda op=char... |
6,036 | def onoperator(selfchar)self eval shiftopnd(self text get()self eval shiftoptr(charself text set(self eval topopnd()self erase push opnd on left eval exprs to leftpush optrshow opnd|result erased on next opnd|'(def onmakecmdline(self)new toplevel(new top-level window new title('pycalc command line'arbitrary python code... |
6,037 | self help(def onhist(self)show recent calcs log popup from tkinter scrolledtext import scrolledtext new toplevel(ok button(newtext="ok"command=new destroyok pack(pady= side=bottomtext scrolledtext(newbg='beige'text insert(' 'self eval gethist()text see(endtext pack(expand=yesfill=bothor pp gui tour make new window pack... |
6,038 | or pop()or del [- def topopnd(self)return self opnd[- top operand (end of listdef open(self)self optr append('('treat '(like an operator def close(self)self shiftoptr(')'self optr[- :[on ')pop downto highest '(ok if emptystays empty popor added again by optr def closeall(self)while self optrforce rest on 'evalself redu... |
6,039 | self hist append(coderesult none return result try stmtnone def gethist(self)return '\njoin(self histdef getcalcargs()from sys import argv get cmdline args in dict config {ex-bg black -fg red for arg in argv[ :]font not yet supported if arg in ['-bg''-fg']-bg red-{'bg':'red'tryconfig[arg[ :]argv[argv index(arg exceptpa... |
6,040 | import sys if len(sys argv= calculator_test py root tk(run calcs in same process calcgui(toplevel()each in new toplevel window calccontainer(toplevel()calcsubclass(toplevel()button(roottext='quit'command=root quitpack(root mainloop(if len(sys argv= calculator_testl py calcgui(mainloop(as standalone window (default root... |
6,041 | top and bottom of the window--but the concept is widely applicable you could reuse the calculator' class by attaching it to any gui that needs calculator and customize it with subclasses arbitrarily it' reusable widget adding new buttons in new components one obvious way to reuse the calculator is to add additional exp... |
6,042 | self calc text set(self calc eval runstring('pi')if __name__ ='__main__'root tk(button(roottop'quit'root quitcalcguiplus(**getcalcargs()mainloop(-bg,-fg to calcgui because pycalc is coded as python classyou can always achieve similar effect by extending pycalc in new subclass instead of embedding itas shown in example ... |
6,043 | issues they could instead convert the entry' text to number and do real mathbut python does all the work automatically when expression strings are run raw also note that the buttons added by these scripts simply operate on the current value in the entry fieldimmediately that' not quite the same as expression operators ... |
6,044 | this concludes our python language material in this book the next and final technical of the text takes us on tour of techniques for integrating python with programs written in compiled languages like and +not everyone needs to know how to do thisso some readers may wish to skip ahead to the book' conclusion in at this... |
6,045 | in closinghere' less tangible but important aspect of python programming common remark among new users is that it' easy to "say what you meanin python without getting bogged down in complex syntax or obscure rules it' programmer-friendly language in factit' not too uncommon for python programs to run on the first attem... |
6,046 | python/ integration " am lost at cthroughout this bookour programs have all been written in python code we have used interfaces to services outside pythonand we've coded reusable tools in the python languagebut all our work has been done in python itself despite our programsscale and utilitythey've been python through ... |
6,047 | complex or proprietary languages in this last technical of this bookwe're going to take brief look at tools for interfacing with -language componentsand discuss both python' ability to be used as an embedded language tool in other systemsand its interfaces for extending python scripts with new modules implemented in -c... |
6,048 | python codea system can be modified without shipping or building its full source code for instancesome programs provide python customization layer that can be used to modify the program on site by modifying python code embedding is also sometimes used to route events to python-coded callback handlers python gui toolkit... |
6,049 | bookwe called out to library through the extending api when our gui' user later clicked those buttonsthe gui library caught the event and routed it to our python functions with embedding although most of the details are hidden to python codecontrol jumps often and freely between languages in such systems python has an ... |
6,050 | layer is responsible for converting arguments passed from python to form and for converting results from to python form python scripts simply import extensions and use them as though they were really coded in python because code does all the translation workthe interface is very seamless and simple in python scripts mo... |
6,051 | else strcpy(result"hello")strcat(resultfrompython)return py_buildvalue(" "result)/build up string */add passed python string */convert -python */registration table *static pymethoddef hello_methods[{"message"messagemeth_varargs"func doc"}{nullnull null}/name&funcfmtdoc */end of table marker */module definition structur... |
6,052 | platforms are analogous but will vary as we learned in cygwin provides unix-like environment and libraries on windows to work along with the examples hereeither install cygwin on your windows platformor change the makefiles listed per your compiler and platform requirements be sure to include the path to python' instal... |
6,053 | or pyc this time around--the only obvious way you can tell it' librarydir(helloc module attributes ['__doc__''__file__''__name__''__package__''message'hello __name__hello __file__ ('hello''hello dll'hello message hello hello __doc__ 'mod dochello message __doc__ 'func doca function object module object docstrings in co... |
6,054 | resulting dll shows up in build subdir from distutils core import setupextension setup(ext_modules=[extension('hello'['hello '])]this is python script that specifies compilation of the extension using tools in the distutils package-- standard part of python that is used to buildinstalland distribute python extensions c... |
6,055 | /******************************************************************** simple library filewith single function"message"which is to be made available for use in python programs there is nothing about python here--this function can be called from programas well as python (with glue code************************************... |
6,056 | description file (usually with suffixor / +header or source file interface files like this one are the most common input formthey can contain comments in or +formattype declarations just like standard header filesand swig directives that all start with for example%module sets the module' name as known to python importe... |
6,057 | $(clib)/hellolib $(clib)/hellolib $(clib)/hellolib gcc $(clib)/hellolib - - $(clib- - $(clib)/hellolib cleanforcerm - dll pyc core rm - dll pyc core hellolib_wrap hellowrap py when run on the hellolib input file by this makefileswig generates two fileshellolib_wrap the generated extension module glue code file hellowra... |
6,058 | internallyas usual in developmentyou may have to barter with the makefile to get it to work on your system once you've run the makefilethoughyou are finished the generated module is used exactly like the manually coded version shown beforeexcept that swig has taken care of the complicated parts automatically function c... |
6,059 | #include #include /***********************/ module functions */***********************static pyobject wrap_getenv(pyobject *selfpyobject *argschar *varname*varvaluepyobject *returnobj null/returns object */self not used */args from python */null=exception *if (pyarg_parse(args"( )"&varname)/python - *varvalue getenv(va... |
6,060 | / module definition */*************************static struct pymoduledef cenvironmodule pymoduledef_head_init"cenviron"/name of module *"cenviron doc"/module documentationmay be null *- /size of per-interpreter module state- =in global vars *cenviron_methods /link to methods table *}/*************************/ module i... |
6,061 | in example - builds the source code for dynamic binding on imports example - pp \integrate\extend\cenviron\makefile cenviron #################################################################compile cenviron into cenviron dll-- shareable object file on cygwinwhich is loaded dynamically when first imported ##############... |
6,062 | some of these calls are made by linked-in codenot by pythoni changed user in the shell prior to this session with an export command)/pp /integrate/extend/cenvironpython import os os environ['user'initialized from the shell 'skipperfrom cenviron import getenvputenv direct library call access getenv('user''skipperputenv(... |
6,063 | import os from cenviron import getenvputenv class envwrapperdef __setattr__(selfnamevalue)os environ[namevalue putenv(namevaluedef __getattr__(selfname)value getenv(nameos environ[namevalue return value env envwrapper(get module' methods wrap in python class on writesenv name=value put in os environ too on readsenv nam... |
6,064 | its output as beforesimply add swig step to your makefile and compile its output file into shareable object for dynamic linkingand you're in business example - is cygwin makefile that does the job example - pp \integrate\extend\swig\environ\makefile environ-swig build environ extension from swig generated code pylib /u... |
6,065 | turns out there' good causethe library' putenv wants string of the form "user=gilliganto be passedwhich becomes part of the environment in codethis means we must create new piece of memory to pass inwe used malloc in example - to satisfy this constraint howeverthere' no simple and direct way to guarantee this on the py... |
6,066 | would be used only from +thensimply run swig in your makefile to scan the +class declaration and compile and link its output the end result is that by importing the shadow class in your python scriptsyou can utilize +classes as though they were really coded in python not only can python programs make and use instances ... |
6,067 | data startprintf("number% \ "data)/python print goes to stdout /orcout <"number<data <endlnumber::~number(printf("~number% \ "data)void number::add(int valuedata +valueprintf("add % \ "value)void number::sub(int valuedata -valueprintf("sub % \ "value)int number::square(return data data/if print labelfflush(stdoutor cou... |
6,068 | num->display()cout <num <endldelete num/print raw instance ptr /run destructor you can use the +command-line +compiler program to compile and run this code on cygwin (it' the same on linuxif you don' use similar systemyou'll have to extrapolatethere are far too many +compiler differences to list here type the compile c... |
6,069 | generate two different python modules againnumber_wrap cxx +extension module with class accessor functions number py python shadow class module that wraps accessor functions the former must be compiled into binary library the latter imports and uses the former' compiled form and is the file that python scripts ultimate... |
6,070 | $(swig- +-python number number pynumber $(swig- +-python number wrapped +class code number onumber cxx number +number cxx - - -wno-deprecated non python test cxxtestg+main cxx number cxx -wno-deprecated cleanforcerm - pyc dll core exe rm - pyc dll core exe number_wrap cxx number py as usualrun this makefile to generate... |
6,071 | num sub( num display(num saves the +'thispointer res num square(print('square'resconverted +int return value num data val num data print('data'valprint('data+ 'val set +data membergenerated __setattr__ get +data membergenerated __getattr__ returns normal python integer object num display(print(numdel num runs repr in s... |
6,072 | number_sub(num number_display(numprint(number_square(num)use accessor functions in the module number_data_set(num print(number_data_get(num)number_display(numprint(numdelete_number(numthis script generates essentially the same output as main pybut it' been slightly simplifiedand the +class instance is something lower l... |
6,073 | num data print(num datanum display(num mul( num display(print(numdel num mul(is implemented in python repr from shadow superclass now we get extra messages out of add callsand mul changes the +class' data member automatically when it assigns self data--the python code extends the +code/pp /integrate/extend/swig/shadowp... |
6,074 | >> display(number= add( dataadd display(number= call +method (like + ->display()fetch +data membercall +method data data data display(number= set +data member records the +this pointer square( square(ttype( ( method with return value type is class in python naturallythis example uses small +class to underscore the basi... |
6,075 | tools installed separatelythough python and later incorporates the ctypes extension as standard library module sip just as sip is smaller swig in the drinking worldso too is the sip system lighter alternative to swig in the python world (in factit was named on purpose for the jokeaccording to its web pagesip makes it e... |
6,076 | developing new extensions from scratch writing interface code for large libraries can be more involved than the code generation approaches of swig and sipbut it' easier than manually wrapping libraries and may afford greater control than fully automated wrapping tool in additionthe py+and older pyste systems provide bo... |
6,077 | compilers moreoverthe py and pyfort systems provide integration with fortran codeand other tools provide access to languages such as delphi and objective- among thesethe pyobjc project aims to provide bridge between python and objective-cthis supports writing cocoa gui applications on mac os in python search the web fo... |
6,078 | control language (what some call "macrolanguagealthough embedding is mostly presented in isolation herekeep in mind that python' integration support is best viewed as whole system' structure usually determines an appropriate integration approachc extensionsembedded code callsor both to wrap upthis concludes by discussi... |
6,079 | python equivalent pyobject_getattrstring getattr(objattrpyobject_setattrstring setattr(objattrvalpyobject_callobject funcobj(*argstuplepyeval_callobject funcobj(*argstuplepyrun_string eval(exprstr)exec(stmtstrpyrun_file exec(open(filename(read()because embedding relies on api call selectionbecoming familiar with the py... |
6,080 | program the actual python code run from can come from wide variety of sourcescode strings might be loaded from filesobtained from an interactive user at console or guifetched from persistent databases and shelvesparsed out of html or xml filesread over socketsbuilt or hardcoded in programpassed to extension functions f... |
6,081 | when run as separate programsfiles can also employ inter-process communication (ipctechniques naturallyall embedded code forms can also communicate with using general systemlevel toolsfilessocketspipesand so on these techniques are generally less direct and slowerthough herewe are still interested in in-process functio... |
6,082 | perhaps the simplest way to run python code from is by calling the pyrun_simple string api function with itc programs can execute python programs represented as character string arrays this call is also very limitedall code runs in the same namespace (the module __main__)the code strings must be python statements (not ... |
6,083 | standard library todayeverything in python that you need in is compiled into single python library file when the interpreter is built ( libpython dll on cygwinthe program' main function comes from your codeand depending on your platform and the extensions installed in your pythonyou may also need to link any external l... |
6,084 | all$(basicsembedexeembedo gcc embed$ - $(pylib-lpython - - $embedoembedc gcc embed$ - - - $(pyinccleanrm - pyc $(basicscore on some platformsyou may need to also link in other libraries because the python library file used may have been built with external dependencies enabled and required in factyou may have to link i... |
6,085 | naturallystrings of python code run by probably would not be hardcoded in program file like this they might instead be loaded from text file or guiextracted from html or xml filesfetched from persistent database or socketand so on with such external sourcesthe python code strings that are run from could be changed arbi... |
6,086 | __import__ built-in function the pyrun_string call is the one that actually runs code herethough it takes code stringa parser mode flagand dictionary object pointers to serve as the global and local namespaces for running the code string the mode flag can be py_eval_input to run an expression or py_file_input to run st... |
6,087 | namespace to serve as input for python print statement string because the string execution call in this version lets you specify namespacesyou can better partition the embedded code your system runs--each grouping can have distinct namespace to avoid overwriting other groupsvariables and because this call returns resul... |
6,088 | converts values to python objects we used both of the data conversion functions earlier in this in extension modules the pyeval_callobject call in this version of the example is the key point hereit runs the imported function with tuple of argumentsmuch like the python func(*argscall syntax the python function' return ... |
6,089 | transform function is function argument herenot preset global variable notice that message is fetched as module attribute this timeinstead of by running its name as code stringas this showsthere is often more than one way to accomplish the same goals with different api calls running functions in modules like this is si... |
6,090 | /make new dictionary for code string namespace *#include main(int cvalpyobject *pdict*pvalprintf("embed-dict\ ")py_initialize()/make new namespace *pdict pydict_new()pydict_setitemstring(pdict"__builtins__"pyeval_getbuiltins())pydict_setitemstring(pdict" "pylong_fromlong( ))pyrun_string(" "py_file_inputpdictpdict)pyrun... |
6,091 | for running code are generally required to have __builtins__ link to the built-in scope searched last for name lookupsset with code of this formpydict_setitemstring(pdict"__builtins__"pyeval_getbuiltins())this is esotericand it is normally handled by python internally for modules and builtins like the exec function for... |
6,092 | pdict pydict_new()if (pdict =nullreturn - pydict_setitemstring(pdict"__builtins__"pyeval_getbuiltins())/precompile strings of code to bytecode objects *pcode py_compilestring(codestr ""py_file_input)pcode py_compilestring(codestr ""py_eval_input)pcode py_compilestring(codestr ""py_file_input)/run compiled bytecode in n... |
6,093 | in the embedding examples thus farc has been running and calling python code from standard main program flow of control things are not always so simplethoughin some casesprograms are modeled on an event-driven architecture in which code is executed only in response to some sort of event the event might be an end user c... |
6,094 | python callback handlerswhich are later run with embedding interfaces in response to gui events you can study tkinter' implementation in the python source distribution for more detailsits tk library interface logic makes it somewhat challenging readbut the basic model it employs is straightforward registration implemen... |
6,095 | if (pres !null/use and decref handler result *pyarg_parse(pres" "&cres)printf("% \ "cres)py_decref(pres)/*****************************************************/ python extension module to register handlers */python imports this module to set handler objects */*****************************************************static p... |
6,096 | that embeds python (though could just as well be on topto compile it into dynamically loaded module filerun the makefile in example - on cygwin (and use something similar on other platformsas we learned earlier in this the resulting cregister dll file will be loaded when first imported by python script if it is placed ... |
6,097 | python calls extension module to register handlerstrigger events ######################################import cregister print('\ntest :'cregister sethandler(callback for in range( )cregister triggerevent(print('\ntest :'cregister sethandler(callback for in range( )cregister triggerevent(register callback function simul... |
6,098 | trace through this example' output and code for more illumination herewe're moving on to the last quick example we have time and space to explore--in the name of symmetryusing python classes from using python classes in earlier in this we learned how to use +classes in python by wrapping them with swig but what about g... |
6,099 | takes bit more code the file in example - implements these steps by arranging calls to the appropriate python api tools example - pp \integrate\embed\pyclass\objects #include #include main(/run objects with low-level calls *char *arg ="sir"*arg ="robin"*cstrpyobject *pmod*pclass*pargs*pinst*pmeth*pres/instance module k... |
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