mirror of https://github.com/python/cpython
Docs for the PEP 264 changes.
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@ -60,9 +60,8 @@ Returns a code object (the same as \code{compile(\var{source},
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\var{filename}, \var{symbol})}) if the command is complete and
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valid; \code{None} if the command is incomplete; raises
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\exception{SyntaxError} if the command is complete and contains a
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syntax error, or raises \exception{OverflowError} if the command
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includes a numeric constant which exceeds the range of the
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appropriate numeric type.
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syntax error, or raises \exception{OverflowError} or
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\exception{ValueError} if the command cotains an invalid literal.
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\end{funcdesc}
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@ -5,14 +5,29 @@
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\declaremodule{standard}{codeop}
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\sectionauthor{Moshe Zadka}{moshez@zadka.site.co.il}
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\sectionauthor{Michael Hudson}{mwh@python.net}
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\modulesynopsis{Compile (possibly incomplete) Python code.}
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The \module{codeop} module provides a function to compile Python code
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with hints on whether it is certainly complete, possibly complete or
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definitely incomplete. This is used by the \refmodule{code} module
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and should not normally be used directly.
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The \module{codeop} module provides utilities upon which the Python
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read-eval-print loop can be emulated -- as in the \refmodule{code}
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module. As a result, you probably don't want to use the module
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directly -- if you want to include such a loop in your program you
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probably want to use the \refmodule{code} instead.
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The \module{codeop} module defines the following function:
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There are two parts to this job:
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\begin{list}
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\listitem Being able to tell if a line of input completes a Python
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statement -- in short telling whether to print ``>>> '' or
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``... '' next.
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\listitem Remembering which future statements the user has entered, so
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subsequent input can be compiled wiht these in effect.
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\end{list}
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The \module{codeop} module provides a way of doing each of these
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things, and a way of doing them both.
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To do just the former:
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\begin{funcdesc}{compile_command}
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{source\optional{, filename\optional{, symbol}}}
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@ -25,8 +40,8 @@ code, but is a prefix of valid Python code.
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If there is a problem with \var{source}, an exception will be raised.
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\exception{SyntaxError} is raised if there is invalid Python syntax,
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and \exception{OverflowError} if there is an invalid numeric
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constant.
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and \exception{OverflowError} or \exception{ValueError} if there is an
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invalid literal.
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The \var{symbol} argument determines whether \var{source} is compiled
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as a statement (\code{'single'}, the default) or as an expression
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@ -41,3 +56,48 @@ error. For example, a backslash followed by two newlines may be
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followed by arbitrary garbage. This will be fixed once the API
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for the parser is better.
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\end{funcdesc}
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\begin{classdesc}{Compile}{}
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Instances of this class have \method{__call__} methods indentical in
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signature to the built-in function \function{compile}, but with the
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difference that if the instance compiles program text containing a
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\module{__future__} statement, the instance 'remembers' and compiles
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all subsequent program texts with the statement in force.
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\end{classdesc}
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\begin{classdesc}{CommandCompiler}{}
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Instances of this class have \method{__call__} methods identical in
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signature to \function{compile_command}; the difference is that if the
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instance compiles program text containing a \method{__future__}
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statement, the instance 'remembers' and compiles all subsequent
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program texts with the statement in force.
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\end{classdesc}
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A note on version compatibility: the \class{Compile} and
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\class{CommandCompiler} are new in Python 2.2. If you want to enable
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the future-tracking features of 2.2 but also retain compatibility with
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2.1 and earlier versions of Python you can either write
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\begin{verbatim}
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try:
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from codeop import CommandCompiler
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compile_command = CommandCompiler()
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del CommandCompiler
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except ImportError:
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from codeop import compile_command
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\end{verbatim}
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which is a low-impact change, but introduces possibly unwanted global
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state into your program, or you can write:
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\begin{verbatim}
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try:
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from codeop import CommandCompiler
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except ImportError:
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def CommandCompiler():
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from codeop import compile_command
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return compile_comamnd
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\end{verbatim}
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and then call \code{CommandCompiler} every time you need a fresh
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compiler object.
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@ -118,7 +118,8 @@ class instances are callable if they have a \method{__call__()} method.
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operations.
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\end{funcdesc}
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\begin{funcdesc}{compile}{string, filename, kind}
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\begin{funcdesc}{compile}{string, filename, kind\optional{,
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flags\optional{, dont_inherit}}}
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Compile the \var{string} into a code object. Code objects can be
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executed by an \keyword{exec} statement or evaluated by a call to
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\function{eval()}. The \var{filename} argument should
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@ -130,6 +131,24 @@ class instances are callable if they have a \method{__call__()} method.
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expression, or \code{'single'} if it consists of a single
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interactive statement (in the latter case, expression statements
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that evaluate to something else than \code{None} will printed).
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The optional arguments \var{flags} and \optional{dont_inherit}
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(which are new in Python 2.2) control which future statements (see
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\pep{236}) affect the compilation of \var{string}. If neither is
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present (or both are zero) the code is compiled with those future
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statements that are in effect in the code that is calling compile.
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If the \var{flags} argument is given and \var{dont_inherit} is not
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(or is zero) then the future statements specified by the \var{flags}
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argument are used in addition to those that would be used anyway.
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If \var{dont_inherit} is a non-zero integer then the \var{flags}
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argument is it -- the future statements in effect around the call to
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compile are ignored.
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Future statemants are specified by bits which can be bitwise or-ed
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together to specify multiple statements. The bitfield required to
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specify a given feature can be found as the \member{compiler_flag}
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attribute on the \class{_Feature} instance in the
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\module{__future__} module.
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\end{funcdesc}
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\begin{funcdesc}{complex}{real\optional{, imag}}
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@ -40,14 +40,17 @@ lines that can appear before a future statement are:
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\end{itemize}
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The only feature recognized by Python 2.1 is \samp{nested_scopes}.
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The features recognized by Python 2.2 are \samp{generators},
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\samp{division} and \samp{nested_scopes}. \samp{nested_scopes}
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is redundant in 2.2 as the nested scopes feature is active by default.
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A future statement is recognized and treated specially at compile time:
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Changes to the semantics of core constructs are often implemented by
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generating different code. It may even be the case that a new feature
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introduces new incompatible syntax (such as a new reserved word), in
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which case the compiler may need to parse the module differently. Such
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decisions cannot be pushed off until runtime.
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A future statement is recognized and treated specially at compile
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time: Changes to the semantics of core constructs are often
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implemented by generating different code. It may even be the case
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that a new feature introduces new incompatible syntax (such as a new
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reserved word), in which case the compiler may need to parse the
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module differently. Such decisions cannot be pushed off until
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runtime.
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For any given release, the compiler knows which feature names have been
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defined, and raises a compile-time error if a future statement contains
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@ -72,8 +75,11 @@ no special semantics or syntax restrictions.
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Code compiled by an exec statement or calls to the builtin functions
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\function{compile()} and \function{execfile()} that occur in a module
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\module{M} containing a future statement will use the new syntax or
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semantics associated with the future statement.
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\module{M} containing a future statement will, by default, use the new
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syntax or semantics associated with the future statement. This can,
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starting with Python 2.2 be controlled by optional arguments to
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\function{compile()} --- see the documentation of that function in the
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library reference for details.
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A future statement typed at an interactive interpreter prompt will
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take effect for the rest of the interpreter session. If an
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@ -110,7 +116,8 @@ is executed.
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Each statment in \file{__future__.py} is of the form:
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\begin{verbatim}
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FeatureName = "_Feature(" OptionalRelease "," MandatoryRelease ")"
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FeatureName = "_Feature(" OptionalRelease "," MandatoryRelease ","
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CompilerFlag ")"
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\end{verbatim}
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where, normally, OptionalRelease is less then MandatoryRelease, and
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@ -143,6 +150,11 @@ feature got dropped.
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Instances of class \class{_Feature} have two corresponding methods,
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\method{getOptionalRelease()} and \method{getMandatoryRelease()}.
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CompilerFlag is the (bitfield) flag that should be passed in the
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fourth argument to the builtin function \function{compile()} to enable
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the feature in dynamically compiled code. This flag is stored in the
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\member{compiler_flag} attribute on \class{_Future} instances.
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No feature description will ever be deleted from \module{__future__}.
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\section{Nested scopes \label{nested-scopes}}
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