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author | Georg Brandl <georg@python.org> | 2007-08-15 14:28:22 (GMT) |
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committer | Georg Brandl <georg@python.org> | 2007-08-15 14:28:22 (GMT) |
commit | 116aa62bf54a39697e25f21d6cf6799f7faa1349 (patch) | |
tree | 8db5729518ed4ca88e26f1e26cc8695151ca3eb3 /Doc/library/code.rst | |
parent | 739c01d47b9118d04e5722333f0e6b4d0c8bdd9e (diff) | |
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Move the 3k reST doc tree in place.
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diff --git a/Doc/library/code.rst b/Doc/library/code.rst new file mode 100644 index 0000000..4e00639 --- /dev/null +++ b/Doc/library/code.rst @@ -0,0 +1,167 @@ + +:mod:`code` --- Interpreter base classes +======================================== + +.. module:: code + :synopsis: Facilities to implement read-eval-print loops. + + + +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]) + + 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 the dictionary 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[, filename]]) + + 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. + + +.. function:: interact([banner[, readfunc[, local]]]) + + 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:`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. The :meth:`interact` method of the instance is then run + with *banner* passed as the banner to use, if provided. The console object is + discarded after use. + + +.. function:: compile_command(source[, filename[, symbol]]) + + 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 either ``'single'`` (the default) or + ``'eval'``. + + 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[, symbol]]) + + 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 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]) + + 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. + + +.. 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]) + + 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!). + + +.. 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:`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. + |