# 27.1 `code` -- Interpreter base classes

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 `InteractiveInterpreter` and adds prompting using the familiar `sys.ps1` and `sys.ps2`, and input buffering.

`interact`( | [banner[, readfunc[, local]]])

  Convenience function to run a read-eval-print loop. This creates a new instance of `InteractiveConsole` and sets readfunc to be used as the `raw_input()` method, if provided. If local is provided, it is passed to the `InteractiveConsole` constructor for use as the default namespace for the interpreter loop. The `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.

`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 `SyntaxError` if the command is complete and contains a syntax error, or raises `OverflowError` or `ValueError` if the command contains an invalid literal.