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authorcinap_lenrek <cinap_lenrek@localhost>2011-05-03 11:25:13 +0000
committercinap_lenrek <cinap_lenrek@localhost>2011-05-03 11:25:13 +0000
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+\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 Python
+read-eval-print loop can be emulated, as is done in the
+\refmodule{code} module. As a result, you probably don't want to use
+the module directly; if you want to include such a loop in your
+program 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 these
+things, 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 Python
+code and return a code object if \var{source} is valid
+Python code. In that case, the filename attribute of the code object
+will be \var{filename}, which defaults to \code{'<input>'}.
+Returns \code{None} if \var{source} is \emph{not} valid Python
+code, 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 an
+invalid literal.
+
+The \var{symbol} argument determines whether \var{source} is compiled
+as 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 parsing
+with a successful outcome before reaching the end of the source;
+in this case, trailing symbols may be ignored instead of causing an
+error. For example, a backslash followed by two newlines may be
+followed by arbitrary garbage. This will be fixed once the API
+for the parser is better.
+\end{funcdesc}
+
+\begin{classdesc}{Compile}{}
+Instances of this class have \method{__call__()} methods identical in
+signature to the built-in function \function{compile()}, but with the
+difference that if the instance compiles program text containing a
+\module{__future__} statement, the instance 'remembers' and compiles
+all subsequent program texts with the statement in force.
+\end{classdesc}
+
+\begin{classdesc}{CommandCompiler}{}
+Instances of this class have \method{__call__()} methods identical in
+signature to \function{compile_command()}; the difference is that if
+the instance compiles program text containing a \code{__future__}
+statement, the instance 'remembers' and compiles all subsequent
+program 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 enable
+the future-tracking features of 2.2 but also retain compatibility with
+2.1 and earlier versions of Python you can either write
+
+\begin{verbatim}
+try:
+ from codeop import CommandCompiler
+ compile_command = CommandCompiler()
+ del CommandCompiler
+except ImportError:
+ from codeop import compile_command
+\end{verbatim}
+
+which is a low-impact change, but introduces possibly unwanted global
+state into your program, or you can write:
+
+\begin{verbatim}
+try:
+ from codeop import CommandCompiler
+except ImportError:
+ def CommandCompiler():
+ from codeop import compile_command
+ return compile_command
+\end{verbatim}
+
+and then call \code{CommandCompiler} every time you need a fresh
+compiler object.