.. highlightlang:: none .. _using-on-general: Command line and environment ============================ The CPython interpreter scans the command line and the environment for various settings. .. note:: Other implementations' command line schemes may differ. See :ref:`implementations` for further resources. .. _using-on-cmdline: Command line ------------ When invoking Python, you may specify any of these options:: python [-dEiOQsStuUvxX3?] [-c command | -m module-name | script | - ] [args] The most common use case is, of course, a simple invocation of a script:: python myscript.py .. _using-on-interface-options: Interface options ~~~~~~~~~~~~~~~~~ The interpreter interface resembles that of the UNIX shell, but provides some additional methods of invocation: * When called with standard input connected to a tty device, it prompts for commands and executes them until an EOF (an end-of-file character, you can produce that with *Ctrl-D* on UNIX or *Ctrl-Z, Enter* on Windows) is read. * When called with a file name argument or with a file as standard input, it reads and executes a script from that file. * When called with a directory name argument, it reads and executes an appropriately named script from that directory. * When called with ``-c command``, it executes the Python statement(s) given as *command*. Here *command* may contain multiple statements separated by newlines. Leading whitespace is significant in Python statements! * When called with ``-m module-name``, the given module is located on the Python module path and executed as a script. In non-interactive mode, the entire input is parsed before it is executed. An interface option terminates the list of options consumed by the interpreter, all consecutive arguments will end up in :data:`sys.argv` -- note that the first element, subscript zero (``sys.argv[0]``), is a string reflecting the program's source. .. cmdoption:: -c Execute the Python code in *command*. *command* can be one ore more statements separated by newlines, with significant leading whitespace as in normal module code. If this option is given, the first element of :data:`sys.argv` will be ``"-c"`` and the current directory will be added to the start of :data:`sys.path` (allowing modules in that directory to be imported as top level modules). .. cmdoption:: -m Search :data:`sys.path` for the named module and execute its contents as the :mod:`__main__` module. Since the argument is a *module* name, you must not give a file extension (``.py``). The ``module-name`` should be a valid Python module name, but the implementation may not always enforce this (e.g. it may allow you to use a name that includes a hyphen). .. note:: This option cannot be used with builtin modules and extension modules written in C, since they do not have Python module files. However, it can still be used for precompiled modules, even if the original source file is not available. If this option is given, the first element of :data:`sys.argv` will be the full path to the module file. As with the :option:`-c` option, the current directory will be added to the start of :data:`sys.path`. Many standard library modules contain code that is invoked on their execution as a script. An example is the :mod:`timeit` module:: python -mtimeit -s 'setup here' 'benchmarked code here' python -mtimeit -h # for details .. seealso:: :func:`runpy.run_module` The actual implementation of this feature. :pep:`338` -- Executing modules as scripts .. versionadded:: 2.4 .. versionchanged:: 2.5 The named module can now be located inside a package. .. describe:: - Read commands from standard input (:data:`sys.stdin`). If standard input is a terminal, :option:`-i` is implied. If this option is given, the first element of :data:`sys.argv` will be ``"-"`` and the current directory will be added to the start of :data:`sys.path`. .. describe::