538 lines
17 KiB
ReStructuredText
538 lines
17 KiB
ReStructuredText
.. 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 <command>
|
|
|
|
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 <module-name>
|
|
|
|
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:: <script>
|
|
|
|
Execute the Python code contained in *script*, which must be a filesystem
|
|
path (absolute or relative) referring to either a Python file, a directory
|
|
containing a ``__main__.py`` file, or a zipfile containing a
|
|
``__main__.py`` file.
|
|
|
|
If this option is given, the first element of :data:`sys.argv` will be the
|
|
script name as given on the command line.
|
|
|
|
If the script name refers directly to a Python file, the directory
|
|
containing that file is added to the start of :data:`sys.path`, and the
|
|
file is executed as the :mod:`__main__` module.
|
|
|
|
If the script name refers to a directory or zipfile, the script name is
|
|
added to the start of :data:`sys.path` and the ``__main__.py`` file in
|
|
that location is executed as the :mod:`__main__` module.
|
|
|
|
.. versionchanged:: 2.5
|
|
Directories and zipfiles containing a ``__main__.py`` file at the top
|
|
level are now considered valid Python scripts.
|
|
|
|
If no interface option is given, :option:`-i` is implied, ``sys.argv[0]`` is
|
|
an empty string (``""``) and the current directory will be added to the
|
|
start of :data:`sys.path`.
|
|
|
|
.. seealso::
|
|
:ref:`tut-invoking`
|
|
|
|
|
|
Generic options
|
|
~~~~~~~~~~~~~~~
|
|
|
|
.. cmdoption:: -?
|
|
-h
|
|
--help
|
|
|
|
Print a short description of all command line options.
|
|
|
|
.. versionchanged:: 2.5
|
|
The ``--help`` variant.
|
|
|
|
|
|
.. cmdoption:: -V
|
|
--version
|
|
|
|
Print the Python version number and exit. Example output could be::
|
|
|
|
Python 2.5.1
|
|
|
|
.. versionchanged:: 2.5
|
|
The ``--version`` variant.
|
|
|
|
|
|
Miscellaneous options
|
|
~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
.. cmdoption:: -B
|
|
|
|
If given, Python won't try to write ``.pyc`` or ``.pyo`` files on the
|
|
import of source modules. See also :envvar:`PYTHONDONTWRITEBYTECODE`.
|
|
|
|
.. versionadded:: 2.6
|
|
|
|
|
|
.. cmdoption:: -d
|
|
|
|
Turn on parser debugging output (for wizards only, depending on compilation
|
|
options). See also :envvar:`PYTHONDEBUG`.
|
|
|
|
|
|
.. cmdoption:: -E
|
|
|
|
Ignore all :envvar:`PYTHON*` environment variables, e.g.
|
|
:envvar:`PYTHONPATH` and :envvar:`PYTHONHOME`, that might be set.
|
|
|
|
.. versionadded:: 2.2
|
|
|
|
|
|
.. cmdoption:: -i
|
|
|
|
When a script is passed as first argument or the :option:`-c` option is used,
|
|
enter interactive mode after executing the script or the command, even when
|
|
:data:`sys.stdin` does not appear to be a terminal. The
|
|
:envvar:`PYTHONSTARTUP` file is not read.
|
|
|
|
This can be useful to inspect global variables or a stack trace when a script
|
|
raises an exception. See also :envvar:`PYTHONINSPECT`.
|
|
|
|
|
|
.. cmdoption:: -O
|
|
|
|
Turn on basic optimizations. This changes the filename extension for
|
|
compiled (:term:`bytecode`) files from ``.pyc`` to ``.pyo``. See also
|
|
:envvar:`PYTHONOPTIMIZE`.
|
|
|
|
|
|
.. cmdoption:: -OO
|
|
|
|
Discard docstrings in addition to the :option:`-O` optimizations.
|
|
|
|
|
|
.. cmdoption:: -Q <arg>
|
|
|
|
Division control. The argument must be one of the following:
|
|
|
|
``old``
|
|
division of int/int and long/long return an int or long (*default*)
|
|
``new``
|
|
new division semantics, i.e. division of int/int and long/long returns a
|
|
float
|
|
``warn``
|
|
old division semantics with a warning for int/int and long/long
|
|
``warnall``
|
|
old division semantics with a warning for all uses of the division operator
|
|
|
|
.. seealso::
|
|
:file:`Tools/scripts/fixdiv.py`
|
|
for a use of ``warnall``
|
|
|
|
:pep:`238` -- Changing the division operator
|
|
|
|
|
|
.. cmdoption:: -s
|
|
|
|
Don't add user site directory to sys.path
|
|
|
|
.. versionadded:: 2.6
|
|
|
|
.. seealso::
|
|
|
|
:pep:`370` -- Per user site-packages directory
|
|
|
|
|
|
.. cmdoption:: -S
|
|
|
|
Disable the import of the module :mod:`site` and the site-dependent
|
|
manipulations of :data:`sys.path` that it entails.
|
|
|
|
|
|
.. cmdoption:: -t
|
|
|
|
Issue a warning when a source file mixes tabs and spaces for indentation in a
|
|
way that makes it depend on the worth of a tab expressed in spaces. Issue an
|
|
error when the option is given twice (:option:`-tt`).
|
|
|
|
|
|
.. cmdoption:: -u
|
|
|
|
Force stdin, stdout and stderr to be totally unbuffered. On systems where it
|
|
matters, also put stdin, stdout and stderr in binary mode.
|
|
|
|
Note that there is internal buffering in :meth:`file.readlines` and
|
|
:ref:`bltin-file-objects` (``for line in sys.stdin``) which is not influenced
|
|
by this option. To work around this, you will want to use
|
|
:meth:`file.readline` inside a ``while 1:`` loop.
|
|
|
|
See also :envvar:`PYTHONUNBUFFERED`.
|
|
|
|
|
|
.. XXX should the -U option be documented?
|
|
|
|
.. cmdoption:: -v
|
|
|
|
Print a message each time a module is initialized, showing the place
|
|
(filename or built-in module) from which it is loaded. When given twice
|
|
(:option:`-vv`), print a message for each file that is checked for when
|
|
searching for a module. Also provides information on module cleanup at exit.
|
|
See also :envvar:`PYTHONVERBOSE`.
|
|
|
|
|
|
.. cmdoption:: -W arg
|
|
|
|
Warning control. Python's warning machinery by default prints warning
|
|
messages to :data:`sys.stderr`. A typical warning message has the following
|
|
form::
|
|
|
|
file:line: category: message
|
|
|
|
By default, each warning is printed once for each source line where it
|
|
occurs. This option controls how often warnings are printed.
|
|
|
|
Multiple :option:`-W` options may be given; when a warning matches more than
|
|
one option, the action for the last matching option is performed. Invalid
|
|
:option:`-W` options are ignored (though, a warning message is printed about
|
|
invalid options when the first warning is issued).
|
|
|
|
Warnings can also be controlled from within a Python program using the
|
|
:mod:`warnings` module.
|
|
|
|
The simplest form of argument is one of the following action strings (or a
|
|
unique abbreviation):
|
|
|
|
``ignore``
|
|
Ignore all warnings.
|
|
``default``
|
|
Explicitly request the default behavior (printing each warning once per
|
|
source line).
|
|
``all``
|
|
Print a warning each time it occurs (this may generate many messages if a
|
|
warning is triggered repeatedly for the same source line, such as inside a
|
|
loop).
|
|
``module``
|
|
Print each warning only only the first time it occurs in each module.
|
|
``once``
|
|
Print each warning only the first time it occurs in the program.
|
|
``error``
|
|
Raise an exception instead of printing a warning message.
|
|
|
|
The full form of argument is::
|
|
|
|
action:message:category:module:line
|
|
|
|
Here, *action* is as explained above but only applies to messages that match
|
|
the remaining fields. Empty fields match all values; trailing empty fields
|
|
may be omitted. The *message* field matches the start of the warning message
|
|
printed; this match is case-insensitive. The *category* field matches the
|
|
warning category. This must be a class name; the match test whether the
|
|
actual warning category of the message is a subclass of the specified warning
|
|
category. The full class name must be given. The *module* field matches the
|
|
(fully-qualified) module name; this match is case-sensitive. The *line*
|
|
field matches the line number, where zero matches all line numbers and is
|
|
thus equivalent to an omitted line number.
|
|
|
|
.. seealso::
|
|
:mod:`warnings` -- the warnings module
|
|
|
|
:pep:`230` -- Warning framework
|
|
|
|
|
|
.. cmdoption:: -x
|
|
|
|
Skip the first line of the source, allowing use of non-Unix forms of
|
|
``#!cmd``. This is intended for a DOS specific hack only.
|
|
|
|
.. warning:: The line numbers in error messages will be off by one!
|
|
|
|
|
|
.. cmdoption:: -3
|
|
|
|
Warn about Python 3.x incompatibilities. Among these are:
|
|
|
|
* :meth:`dict.has_key`
|
|
* :func:`apply`
|
|
* :func:`callable`
|
|
* :func:`coerce`
|
|
* :func:`execfile`
|
|
* :func:`reduce`
|
|
* :func:`reload`
|
|
|
|
Using these will emit a :exc:`DeprecationWarning`.
|
|
|
|
.. versionadded:: 2.6
|
|
|
|
|
|
|
|
.. _using-on-envvars:
|
|
|
|
Environment variables
|
|
---------------------
|
|
|
|
These environment variables influence Python's behavior.
|
|
|
|
.. envvar:: PYTHONHOME
|
|
|
|
Change the location of the standard Python libraries. By default, the
|
|
libraries are searched in :file:`{prefix}/lib/python{version}` and
|
|
:file:`{exec_prefix}/lib/python{version}`, where :file:`{prefix}` and
|
|
:file:`{exec_prefix}` are installation-dependent directories, both defaulting
|
|
to :file:`/usr/local`.
|
|
|
|
When :envvar:`PYTHONHOME` is set to a single directory, its value replaces
|
|
both :file:`{prefix}` and :file:`{exec_prefix}`. To specify different values
|
|
for these, set :envvar:`PYTHONHOME` to :file:`{prefix}:{exec_prefix}`.
|
|
|
|
|
|
.. envvar:: PYTHONPATH
|
|
|
|
Augment the default search path for module files. The format is the same as
|
|
the shell's :envvar:`PATH`: one or more directory pathnames separated by
|
|
:data:`os.pathsep` (e.g. colons on Unix or semicolons on Windows).
|
|
Non-existent directories are silently ignored.
|
|
|
|
In addition to normal directories, individual :envvar:`PYTHONPATH` entries
|
|
may refer to zipfiles containing pure Python modules (in either source or
|
|
compiled form). Extension modules cannot be imported from zipfiles.
|
|
|
|
The default search path is installation dependent, but generally begins with
|
|
:file:`{prefix}/lib/python{version}`` (see :envvar:`PYTHONHOME` above). It
|
|
is *always* appended to :envvar:`PYTHONPATH`.
|
|
|
|
An additional directory will be inserted in the search path in front of
|
|
:envvar:`PYTHONPATH` as described above under
|
|
:ref:`using-on-interface-options`. The search path can be manipulated from
|
|
within a Python program as the variable :data:`sys.path`.
|
|
|
|
|
|
.. envvar:: PYTHONSTARTUP
|
|
|
|
If this is the name of a readable file, the Python commands in that file are
|
|
executed before the first prompt is displayed in interactive mode. The file
|
|
is executed in the same namespace where interactive commands are executed so
|
|
that objects defined or imported in it can be used without qualification in
|
|
the interactive session. You can also change the prompts :data:`sys.ps1` and
|
|
:data:`sys.ps2` in this file.
|
|
|
|
|
|
.. envvar:: PYTHONY2K
|
|
|
|
Set this to a non-empty string to cause the :mod:`time` module to require
|
|
dates specified as strings to include 4-digit years, otherwise 2-digit years
|
|
are converted based on rules described in the :mod:`time` module
|
|
documentation.
|
|
|
|
|
|
.. envvar:: PYTHONOPTIMIZE
|
|
|
|
If this is set to a non-empty string it is equivalent to specifying the
|
|
:option:`-O` option. If set to an integer, it is equivalent to specifying
|
|
:option:`-O` multiple times.
|
|
|
|
|
|
.. envvar:: PYTHONDEBUG
|
|
|
|
If this is set to a non-empty string it is equivalent to specifying the
|
|
:option:`-d` option. If set to an integer, it is equivalent to specifying
|
|
:option:`-d` multiple times.
|
|
|
|
|
|
.. envvar:: PYTHONINSPECT
|
|
|
|
If this is set to a non-empty string it is equivalent to specifying the
|
|
:option:`-i` option.
|
|
|
|
This variable can also be modified by Python code using :data:`os.environ`
|
|
to force inspect mode on program termination.
|
|
|
|
|
|
.. envvar:: PYTHONUNBUFFERED
|
|
|
|
If this is set to a non-empty string it is equivalent to specifying the
|
|
:option:`-u` option.
|
|
|
|
|
|
.. envvar:: PYTHONVERBOSE
|
|
|
|
If this is set to a non-empty string it is equivalent to specifying the
|
|
:option:`-v` option. If set to an integer, it is equivalent to specifying
|
|
:option:`-v` multiple times.
|
|
|
|
|
|
.. envvar:: PYTHONCASEOK
|
|
|
|
If this is set, Python ignores case in :keyword:`import` statements. This
|
|
only works on Windows.
|
|
|
|
|
|
.. envvar:: PYTHONDONTWRITEBYTECODE
|
|
|
|
If this is set, Python won't try to write ``.pyc`` or ``.pyo`` files on the
|
|
import of source modules.
|
|
|
|
.. versionadded:: 2.6
|
|
|
|
|
|
.. envvar:: PYTHONNOUSERSITE
|
|
|
|
If this is set, Python won't add the user site directory to sys.path
|
|
|
|
.. versionadded:: 2.6
|
|
|
|
.. seealso::
|
|
|
|
:pep:`370` -- Per user site-packages directory
|
|
|
|
|
|
.. envvar:: PYTHONUSERBASE
|
|
|
|
Sets the base directory for the user site directory
|
|
|
|
.. versionadded:: 2.6
|
|
|
|
.. seealso::
|
|
|
|
:pep:`370` -- Per user site-packages directory
|
|
|
|
|
|
.. envvar:: PYTHONEXECUTABLE
|
|
|
|
If this environment variable is set, ``sys.argv[0]`` will be set to its
|
|
value instead of the value got through the C runtime. Only works on
|
|
MacOS X.
|
|
|
|
|
|
Debug-mode variables
|
|
~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Setting these variables only has an effect in a debug build of Python, that is,
|
|
if Python was configured with the :option:`--with-pydebug` build option.
|
|
|
|
.. envvar:: PYTHONTHREADDEBUG
|
|
|
|
If set, Python will print threading debug info.
|
|
|
|
.. versionchanged:: 2.6
|
|
Previously, this variable was called ``THREADDEBUG``.
|
|
|
|
.. envvar:: PYTHONDUMPREFS
|
|
|
|
If set, Python will dump objects and reference counts still alive after
|
|
shutting down the interpreter.
|
|
|
|
|
|
.. envvar:: PYTHONMALLOCSTATS
|
|
|
|
If set, Python will print memory allocation statistics every time a new
|
|
object arena is created, and on shutdown.
|
|
|