\section{\module{codeop} ---         Compile Python code} % LaTeXed from excellent doc-string. \declaremodule{standard}{codeop}\sectionauthor{Moshe Zadka}{moshez@zadka.site.co.il}\sectionauthor{Michael Hudson}{mwh@python.net}\modulesynopsis{Compile (possibly incomplete) Python code.} The \module{codeop} module provides utilities upon which the Pythonread-eval-print loop can be emulated, as is done in the\refmodule{code} module.  As a result, you probably don't want to usethe module directly; if you want to include such a loop in yourprogram you probably want to use the \refmodule{code} module instead. There are two parts to this job:  \begin{enumerate}  \item Being able to tell if a line of input completes a Python         statement: in short, telling whether to print        `\code{>>>~}' or `\code{...~}' next.  \item Remembering which future statements the user has entered, so         subsequent input can be compiled with these in effect.\end{enumerate} The \module{codeop} module provides a way of doing each of thesethings, and a way of doing them both. To do just the former: \begin{funcdesc}{compile_command}                {source\optional{, filename\optional{, symbol}}}Tries to compile \var{source}, which should be a string of Pythoncode and return a code object if \var{source} is validPython code. In that case, the filename attribute of the code objectwill be \var{filename}, which defaults to \code{'<input>'}.Returns \code{None} if \var{source} is \emph{not} valid Pythoncode, but is a prefix of valid Python code. If there is a problem with \var{source}, an exception will be raised.\exception{SyntaxError} is raised if there is invalid Python syntax,and \exception{OverflowError} or \exception{ValueError} if there is aninvalid literal. The \var{symbol} argument determines whether \var{source} is compiledas a statement (\code{'single'}, the default) or as an expression(\code{'eval'}).  Any other value will cause \exception{ValueError} to be raised. \strong{Caveat:}It is possible (but not likely) that the parser stops parsingwith a successful outcome before reaching the end of the source;in this case, trailing symbols may be ignored instead of causing anerror.  For example, a backslash followed by two newlines may befollowed by arbitrary garbage.  This will be fixed once the APIfor the parser is better.\end{funcdesc} \begin{classdesc}{Compile}{}Instances of this class have \method{__call__()} methods identical insignature to the built-in function \function{compile()}, but with thedifference that if the instance compiles program text containing a\module{__future__} statement, the instance 'remembers' and compilesall subsequent program texts with the statement in force.\end{classdesc} \begin{classdesc}{CommandCompiler}{}Instances of this class have \method{__call__()} methods identical insignature to \function{compile_command()}; the difference is that ifthe instance compiles program text containing a \code{__future__}statement, the instance 'remembers' and compiles all subsequentprogram texts with the statement in force.\end{classdesc} A note on version compatibility: the \class{Compile} and\class{CommandCompiler} are new in Python 2.2.  If you want to enablethe future-tracking features of 2.2 but also retain compatibility with2.1 and earlier versions of Python you can either write \begin{verbatim}try:    from codeop import CommandCompiler    compile_command = CommandCompiler()    del CommandCompilerexcept ImportError:    from codeop import compile_command\end{verbatim} which is a low-impact change, but introduces possibly unwanted globalstate into your program, or you can write: \begin{verbatim}try:    from codeop import CommandCompilerexcept ImportError:    def CommandCompiler():        from codeop import compile_command        return compile_command\end{verbatim} and then call \code{CommandCompiler} every time you need a freshcompiler object.