mirror of
https://github.com/python/cpython.git
synced 2024-11-30 18:51:15 +01:00
e870c852c0
* expand on What's New entry for PEP 667 (including porting notes) * define 'optimized scope' as a glossary term * cover comprehensions and generator expressions in locals() docs * review all mentions of "locals" in documentation (updating if needed) * review all mentions of "f_locals" in documentation (updating if needed)
192 lines
8.1 KiB
ReStructuredText
192 lines
8.1 KiB
ReStructuredText
:mod:`!code` --- Interpreter base classes
|
|
=========================================
|
|
|
|
.. module:: code
|
|
:synopsis: Facilities to implement read-eval-print loops.
|
|
|
|
**Source code:** :source:`Lib/code.py`
|
|
|
|
--------------
|
|
|
|
The ``code`` module provides facilities to implement read-eval-print loops in
|
|
Python. Two classes and convenience functions are included which can be used to
|
|
build applications which provide an interactive interpreter prompt.
|
|
|
|
|
|
.. class:: InteractiveInterpreter(locals=None)
|
|
|
|
This class deals with parsing and interpreter state (the user's namespace); it
|
|
does not deal with input buffering or prompting or input file naming (the
|
|
filename is always passed in explicitly). The optional *locals* argument
|
|
specifies a mapping to use as the namespace in which code will be executed;
|
|
it defaults to a newly created dictionary with key ``'__name__'`` set to
|
|
``'__console__'`` and key ``'__doc__'`` set to ``None``.
|
|
|
|
|
|
.. class:: InteractiveConsole(locals=None, filename="<console>", local_exit=False)
|
|
|
|
Closely emulate the behavior of the interactive Python interpreter. This class
|
|
builds on :class:`InteractiveInterpreter` and adds prompting using the familiar
|
|
``sys.ps1`` and ``sys.ps2``, and input buffering. If *local_exit* is true,
|
|
``exit()`` and ``quit()`` in the console will not raise :exc:`SystemExit`, but
|
|
instead return to the calling code.
|
|
|
|
.. versionchanged:: 3.13
|
|
Added *local_exit* parameter.
|
|
|
|
.. function:: interact(banner=None, readfunc=None, local=None, exitmsg=None, local_exit=False)
|
|
|
|
Convenience function to run a read-eval-print loop. This creates a new
|
|
instance of :class:`InteractiveConsole` and sets *readfunc* to be used as
|
|
the :meth:`InteractiveConsole.raw_input` method, if provided. If *local* is
|
|
provided, it is passed to the :class:`InteractiveConsole` constructor for
|
|
use as the default namespace for the interpreter loop. If *local_exit* is provided,
|
|
it is passed to the :class:`InteractiveConsole` constructor. The :meth:`~InteractiveConsole.interact`
|
|
method of the instance is then run with *banner* and *exitmsg* passed as the
|
|
banner and exit message to use, if provided. The console object is discarded
|
|
after use.
|
|
|
|
.. versionchanged:: 3.6
|
|
Added *exitmsg* parameter.
|
|
|
|
.. versionchanged:: 3.13
|
|
Added *local_exit* parameter.
|
|
|
|
.. function:: compile_command(source, filename="<input>", symbol="single")
|
|
|
|
This function is useful for programs that want to emulate Python's interpreter
|
|
main loop (a.k.a. the read-eval-print loop). The tricky part is to determine
|
|
when the user has entered an incomplete command that can be completed by
|
|
entering more text (as opposed to a complete command or a syntax error). This
|
|
function *almost* always makes the same decision as the real interpreter main
|
|
loop.
|
|
|
|
*source* is the source string; *filename* is the optional filename from which
|
|
source was read, defaulting to ``'<input>'``; and *symbol* is the optional
|
|
grammar start symbol, which should be ``'single'`` (the default), ``'eval'``
|
|
or ``'exec'``.
|
|
|
|
Returns a code object (the same as ``compile(source, filename, symbol)``) if the
|
|
command is complete and valid; ``None`` if the command is incomplete; raises
|
|
:exc:`SyntaxError` if the command is complete and contains a syntax error, or
|
|
raises :exc:`OverflowError` or :exc:`ValueError` if the command contains an
|
|
invalid literal.
|
|
|
|
|
|
.. _interpreter-objects:
|
|
|
|
Interactive Interpreter Objects
|
|
-------------------------------
|
|
|
|
|
|
.. method:: InteractiveInterpreter.runsource(source, filename="<input>", symbol="single")
|
|
|
|
Compile and run some source in the interpreter. Arguments are the same as for
|
|
:func:`compile_command`; the default for *filename* is ``'<input>'``, and for
|
|
*symbol* is ``'single'``. One of several things can happen:
|
|
|
|
* The input is incorrect; :func:`compile_command` raised an exception
|
|
(:exc:`SyntaxError` or :exc:`OverflowError`). A syntax traceback will be
|
|
printed by calling the :meth:`showsyntaxerror` method. :meth:`runsource`
|
|
returns ``False``.
|
|
|
|
* The input is incomplete, and more input is required; :func:`compile_command`
|
|
returned ``None``. :meth:`runsource` returns ``True``.
|
|
|
|
* The input is complete; :func:`compile_command` returned a code object. The
|
|
code is executed by calling the :meth:`runcode` (which also handles run-time
|
|
exceptions, except for :exc:`SystemExit`). :meth:`runsource` returns ``False``.
|
|
|
|
The return value can be used to decide whether to use ``sys.ps1`` or ``sys.ps2``
|
|
to prompt the next line.
|
|
|
|
|
|
.. method:: InteractiveInterpreter.runcode(code)
|
|
|
|
Execute a code object. When an exception occurs, :meth:`showtraceback` is called
|
|
to display a traceback. All exceptions are caught except :exc:`SystemExit`,
|
|
which is allowed to propagate.
|
|
|
|
A note about :exc:`KeyboardInterrupt`: this exception may occur elsewhere in
|
|
this code, and may not always be caught. The caller should be prepared to deal
|
|
with it.
|
|
|
|
|
|
.. method:: InteractiveInterpreter.showsyntaxerror(filename=None)
|
|
|
|
Display the syntax error that just occurred. This does not display a stack
|
|
trace because there isn't one for syntax errors. If *filename* is given, it is
|
|
stuffed into the exception instead of the default filename provided by Python's
|
|
parser, because it always uses ``'<string>'`` when reading from a string. The
|
|
output is written by the :meth:`write` method.
|
|
|
|
|
|
.. method:: InteractiveInterpreter.showtraceback()
|
|
|
|
Display the exception that just occurred. We remove the first stack item
|
|
because it is within the interpreter object implementation. The output is
|
|
written by the :meth:`write` method.
|
|
|
|
.. versionchanged:: 3.5 The full chained traceback is displayed instead
|
|
of just the primary traceback.
|
|
|
|
|
|
.. method:: InteractiveInterpreter.write(data)
|
|
|
|
Write a string to the standard error stream (``sys.stderr``). Derived classes
|
|
should override this to provide the appropriate output handling as needed.
|
|
|
|
|
|
.. _console-objects:
|
|
|
|
Interactive Console Objects
|
|
---------------------------
|
|
|
|
The :class:`InteractiveConsole` class is a subclass of
|
|
:class:`InteractiveInterpreter`, and so offers all the methods of the
|
|
interpreter objects as well as the following additions.
|
|
|
|
|
|
.. method:: InteractiveConsole.interact(banner=None, exitmsg=None)
|
|
|
|
Closely emulate the interactive Python console. The optional *banner* argument
|
|
specify the banner to print before the first interaction; by default it prints a
|
|
banner similar to the one printed by the standard Python interpreter, followed
|
|
by the class name of the console object in parentheses (so as not to confuse
|
|
this with the real interpreter -- since it's so close!).
|
|
|
|
The optional *exitmsg* argument specifies an exit message printed when exiting.
|
|
Pass the empty string to suppress the exit message. If *exitmsg* is not given or
|
|
``None``, a default message is printed.
|
|
|
|
.. versionchanged:: 3.4
|
|
To suppress printing any banner, pass an empty string.
|
|
|
|
.. versionchanged:: 3.6
|
|
Print an exit message when exiting.
|
|
|
|
|
|
.. method:: InteractiveConsole.push(line)
|
|
|
|
Push a line of source text to the interpreter. The line should not have a
|
|
trailing newline; it may have internal newlines. The line is appended to a
|
|
buffer and the interpreter's :meth:`~InteractiveInterpreter.runsource` method is called with the
|
|
concatenated contents of the buffer as source. If this indicates that the
|
|
command was executed or invalid, the buffer is reset; otherwise, the command is
|
|
incomplete, and the buffer is left as it was after the line was appended. The
|
|
return value is ``True`` if more input is required, ``False`` if the line was
|
|
dealt with in some way (this is the same as :meth:`!runsource`).
|
|
|
|
|
|
.. method:: InteractiveConsole.resetbuffer()
|
|
|
|
Remove any unhandled source text from the input buffer.
|
|
|
|
|
|
.. method:: InteractiveConsole.raw_input(prompt="")
|
|
|
|
Write a prompt and read a line. The returned line does not include the trailing
|
|
newline. When the user enters the EOF key sequence, :exc:`EOFError` is raised.
|
|
The base implementation reads from ``sys.stdin``; a subclass may replace this
|
|
with a different implementation.
|