Georg Brandl | 59d121a | 2007-10-20 18:08:14 +0000 | [diff] [blame] | 1 | .. highlightlang:: none |
| 2 | |
Georg Brandl | 87983f2 | 2007-12-01 23:12:45 +0000 | [diff] [blame^] | 3 | .. _using-on-general: |
| 4 | |
Georg Brandl | 1cddfed | 2007-10-20 18:33:20 +0000 | [diff] [blame] | 5 | Command line and environment |
| 6 | ============================ |
Georg Brandl | 59d121a | 2007-10-20 18:08:14 +0000 | [diff] [blame] | 7 | |
| 8 | The CPython interpreter scans the command line and the environment for various |
| 9 | settings. |
| 10 | |
| 11 | .. note:: |
| 12 | |
| 13 | Other implementation's command line schemes may differ. See |
| 14 | :ref:`implementations` for further resources. |
| 15 | |
| 16 | |
Georg Brandl | 87983f2 | 2007-12-01 23:12:45 +0000 | [diff] [blame^] | 17 | .. _using-on-cmdline: |
| 18 | |
Georg Brandl | 59d121a | 2007-10-20 18:08:14 +0000 | [diff] [blame] | 19 | Command line |
| 20 | ------------ |
| 21 | |
| 22 | When invoking Python, you may specify any of these options:: |
| 23 | |
| 24 | python [-dEiOQStuUvxX3?] [-c command | -m module-name | script | - ] [args] |
| 25 | |
| 26 | The most common use case is, of course, a simple invocation of a script:: |
| 27 | |
| 28 | python myscript.py |
| 29 | |
| 30 | |
| 31 | Interface options |
| 32 | ~~~~~~~~~~~~~~~~~ |
| 33 | |
| 34 | The interpreter interface resembles that of the UNIX shell: |
| 35 | |
| 36 | * When called with standard input connected to a tty device, it prompts for |
| 37 | commands and executes them until an EOF (an end-of-file character, you can |
| 38 | produce that with *Ctrl-D* on UNIX or *Ctrl-Z, Enter* on Windows) is read. |
| 39 | * When called with a file name argument or with a file as standard input, it |
| 40 | reads and executes a script from that file. |
| 41 | * When called with ``-c command``, it executes the Python statement(s) given as |
| 42 | *command*. Here *command* may contain multiple statements separated by |
| 43 | newlines. Leading whitespace is significant in Python statements! |
| 44 | * When called with ``-m module-name``, the given module is searched on the |
| 45 | Python module path and executed as a script. |
| 46 | |
| 47 | In non-interactive mode, the entire input is parsed before it is executed. |
| 48 | |
| 49 | An interface option terminates the list of options consumed by the interpreter, |
| 50 | all consecutive arguments will end up in :data:`sys.argv` -- note that the first |
| 51 | element, subscript zero (``sys.argv[0]``), is a string reflecting the program's |
| 52 | source. |
| 53 | |
| 54 | .. cmdoption:: -c <command> |
| 55 | |
| 56 | Execute the Python code in *command*. *command* can be one ore more |
| 57 | statements separated by newlines, with significant leading whitespace as in |
| 58 | normal module code. |
| 59 | |
| 60 | If this option is given, the first element of :data:`sys.argv` will be |
| 61 | ``"-c"``. |
| 62 | |
| 63 | |
| 64 | .. cmdoption:: -m <module-name> |
| 65 | |
| 66 | Search :data:`sys.path` for the named module and run the corresponding module |
| 67 | file as if it were executed with ``python modulefile.py`` as a script. |
| 68 | |
| 69 | Since the argument is a *module* name, you must not give a file extension |
| 70 | (``.py``). However, the ``module-name`` does not have to be a valid Python |
| 71 | identifer (e.g. you can use a file name including a hyphen). |
| 72 | |
| 73 | .. note:: |
| 74 | |
| 75 | This option cannot be used with builtin modules and extension modules |
| 76 | written in C, since they do not have Python module files. |
| 77 | |
| 78 | If this option is given, the first element of :data:`sys.argv` will be the |
| 79 | full path to the module file. |
| 80 | |
| 81 | Many standard library modules contain code that is invoked on their execution |
| 82 | as a script. An example is the :mod:`timeit` module:: |
| 83 | |
| 84 | python -mtimeit -s 'setup here' 'benchmarked code here' |
| 85 | python -mtimeit -h # for details |
| 86 | |
| 87 | .. seealso:: |
| 88 | :func:`runpy.run_module` |
| 89 | The actual implementation of this feature. |
| 90 | |
| 91 | :pep:`338` -- Executing modules as scripts |
| 92 | |
| 93 | .. versionchanged:: 2.5 |
| 94 | The module name can now include packages. |
| 95 | |
| 96 | |
| 97 | .. describe:: <script> |
| 98 | |
| 99 | Execute the Python code contained in *script*, which must be an (absolute or |
| 100 | relative) file name. |
| 101 | |
| 102 | If this option is given, the first element of :data:`sys.argv` will be the |
| 103 | script file name as given on the command line. |
| 104 | |
| 105 | |
| 106 | .. describe:: - |
| 107 | |
| 108 | Read commands from standard input (:data:`sys.stdin`). If standard input is |
| 109 | a terminal, :option:`-i` is implied. |
| 110 | |
| 111 | If this option is given, the first element of :data:`sys.argv` will be |
| 112 | ``"-"``. |
| 113 | |
| 114 | .. seealso:: |
| 115 | :ref:`tut-invoking` |
| 116 | |
| 117 | |
| 118 | If no script name is given, ``sys.argv[0]`` is an empty string (``""``). |
| 119 | |
| 120 | |
| 121 | Generic options |
| 122 | ~~~~~~~~~~~~~~~ |
| 123 | |
| 124 | .. cmdoption:: -? |
| 125 | -h |
| 126 | --help |
| 127 | |
| 128 | Print a short description of all command line options. |
| 129 | |
| 130 | .. versionadded:: 2.5 |
| 131 | The ``--help`` variant. |
| 132 | |
| 133 | |
| 134 | .. cmdoption:: -V |
| 135 | --version |
| 136 | |
| 137 | Print the Python version number and exit. Example output could be:: |
| 138 | |
| 139 | Python 2.5.1 |
| 140 | |
| 141 | .. versionadded:: 2.5 |
| 142 | The ``--version`` variant. |
| 143 | |
| 144 | |
| 145 | Miscellaneous options |
| 146 | ~~~~~~~~~~~~~~~~~~~~~ |
| 147 | |
| 148 | .. cmdoption:: -d |
| 149 | |
| 150 | Turn on parser debugging output (for wizards only, depending on compilation |
| 151 | options). See also :envvar:`PYTHONDEBUG`. |
| 152 | |
| 153 | |
| 154 | .. cmdoption:: -E |
| 155 | |
Georg Brandl | c5004f3 | 2007-10-20 19:05:45 +0000 | [diff] [blame] | 156 | Ignore all :envvar:`PYTHON*` environment variables, e.g. |
Georg Brandl | 3507333 | 2007-10-20 19:08:36 +0000 | [diff] [blame] | 157 | :envvar:`PYTHONPATH` and :envvar:`PYTHONHOME`, that might be set. |
Georg Brandl | 59d121a | 2007-10-20 18:08:14 +0000 | [diff] [blame] | 158 | |
Georg Brandl | c5004f3 | 2007-10-20 19:05:45 +0000 | [diff] [blame] | 159 | .. versionadded:: 2.2 |
Georg Brandl | 59d121a | 2007-10-20 18:08:14 +0000 | [diff] [blame] | 160 | |
| 161 | |
| 162 | .. cmdoption:: -i |
| 163 | |
| 164 | When a script is passed as first argument or the :option:`-c` option is used, |
| 165 | enter interactive mode after executing the script or the command, even when |
| 166 | :data:`sys.stdin` does not appear to be a terminal. The |
| 167 | :envvar:`PYTHONSTARTUP` file is not read. |
| 168 | |
| 169 | This can be useful to inspect global variables or a stack trace when a script |
| 170 | raises an exception. See also :envvar:`PYTHONINSPECT`. |
| 171 | |
| 172 | |
| 173 | .. cmdoption:: -O |
| 174 | |
| 175 | Turn on basic optimizations. This changes the filename extension for |
Georg Brandl | 5e52db0 | 2007-10-21 10:45:46 +0000 | [diff] [blame] | 176 | compiled (:term:`bytecode`) files from ``.pyc`` to ``.pyo``. See also |
Georg Brandl | 59d121a | 2007-10-20 18:08:14 +0000 | [diff] [blame] | 177 | :envvar:`PYTHONOPTIMIZE`. |
| 178 | |
| 179 | |
| 180 | .. cmdoption:: -OO |
| 181 | |
| 182 | Discard docstrings in addition to the :option:`-O` optimizations. |
| 183 | |
| 184 | |
| 185 | .. cmdoption:: -Q <arg> |
| 186 | |
| 187 | Division control. The argument must be one of the following: |
| 188 | |
| 189 | ``old`` |
| 190 | division of int/int and long/long return an int or long (*default*) |
| 191 | ``new`` |
| 192 | new division semantics, i.e. division of int/int and long/long returns a |
| 193 | float |
| 194 | ``warn`` |
| 195 | old division semantics with a warning for int/int and long/long |
| 196 | ``warnall`` |
| 197 | old division semantics with a warning for all uses of the division operator |
| 198 | |
| 199 | .. seealso:: |
| 200 | :file:`Tools/scripts/fixdiv.py` |
| 201 | for a use of ``warnall`` |
| 202 | |
| 203 | :pep:`238` -- Changing the division operator |
| 204 | |
| 205 | |
| 206 | .. cmdoption:: -S |
| 207 | |
| 208 | Disable the import of the module :mod:`site` and the site-dependent |
| 209 | manipulations of :data:`sys.path` that it entails. |
| 210 | |
| 211 | |
| 212 | .. cmdoption:: -t |
| 213 | |
| 214 | Issue a warning when a source file mixes tabs and spaces for indentation in a |
| 215 | way that makes it depend on the worth of a tab expressed in spaces. Issue an |
| 216 | error when the option is given twice (:option:`-tt`). |
| 217 | |
| 218 | |
| 219 | .. cmdoption:: -u |
| 220 | |
| 221 | Force stdin, stdout and stderr to be totally unbuffered. On systems where it |
| 222 | matters, also put stdin, stdout and stderr in binary mode. |
| 223 | |
Georg Brandl | f4ef23f | 2007-10-30 17:51:18 +0000 | [diff] [blame] | 224 | Note that there is internal buffering in :meth:`file.readlines` and |
Georg Brandl | 59d121a | 2007-10-20 18:08:14 +0000 | [diff] [blame] | 225 | :ref:`bltin-file-objects` (``for line in sys.stdin``) which is not influenced |
| 226 | by this option. To work around this, you will want to use |
Georg Brandl | f4ef23f | 2007-10-30 17:51:18 +0000 | [diff] [blame] | 227 | :meth:`file.readline` inside a ``while 1:`` loop. |
Georg Brandl | 59d121a | 2007-10-20 18:08:14 +0000 | [diff] [blame] | 228 | |
| 229 | See also :envvar:`PYTHONUNBUFFERED`. |
| 230 | |
| 231 | |
| 232 | .. XXX should the -U option be documented? |
| 233 | |
| 234 | .. cmdoption:: -v |
| 235 | |
| 236 | Print a message each time a module is initialized, showing the place |
| 237 | (filename or built-in module) from which it is loaded. When given twice |
| 238 | (:option:`-vv`), print a message for each file that is checked for when |
| 239 | searching for a module. Also provides information on module cleanup at exit. |
| 240 | See also :envvar:`PYTHONVERBOSE`. |
| 241 | |
| 242 | |
| 243 | .. cmdoption:: -W arg |
| 244 | |
| 245 | Warning control. Python's warning machinery by default prints warning |
| 246 | messages to :data:`sys.stderr`. A typical warning message has the following |
| 247 | form:: |
| 248 | |
| 249 | file:line: category: message |
| 250 | |
| 251 | By default, each warning is printed once for each source line where it |
| 252 | occurs. This option controls how often warnings are printed. |
| 253 | |
| 254 | Multiple :option:`-W` options may be given; when a warning matches more than |
| 255 | one option, the action for the last matching option is performed. Invalid |
| 256 | :option:`-W` options are ignored (though, a warning message is printed about |
| 257 | invalid options when the first warning is issued). |
| 258 | |
| 259 | Warnings can also be controlled from within a Python program using the |
| 260 | :mod:`warnings` module. |
| 261 | |
| 262 | The simplest form of argument is one of the following action strings (or a |
| 263 | unique abbreviation): |
| 264 | |
| 265 | ``ignore`` |
| 266 | Ignore all warnings. |
| 267 | ``default`` |
| 268 | Explicitly request the default behavior (printing each warning once per |
| 269 | source line). |
| 270 | ``all`` |
| 271 | Print a warning each time it occurs (this may generate many messages if a |
| 272 | warning is triggered repeatedly for the same source line, such as inside a |
| 273 | loop). |
| 274 | ``module`` |
| 275 | Print each warning only only the first time it occurs in each module. |
| 276 | ``once`` |
| 277 | Print each warning only the first time it occurs in the program. |
| 278 | ``error`` |
| 279 | Raise an exception instead of printing a warning message. |
| 280 | |
| 281 | The full form of argument is:: |
| 282 | |
| 283 | action:message:category:module:line |
| 284 | |
| 285 | Here, *action* is as explained above but only applies to messages that match |
| 286 | the remaining fields. Empty fields match all values; trailing empty fields |
| 287 | may be omitted. The *message* field matches the start of the warning message |
| 288 | printed; this match is case-insensitive. The *category* field matches the |
| 289 | warning category. This must be a class name; the match test whether the |
| 290 | actual warning category of the message is a subclass of the specified warning |
| 291 | category. The full class name must be given. The *module* field matches the |
| 292 | (fully-qualified) module name; this match is case-sensitive. The *line* |
| 293 | field matches the line number, where zero matches all line numbers and is |
| 294 | thus equivalent to an omitted line number. |
| 295 | |
| 296 | .. seealso:: |
| 297 | |
| 298 | :pep:`230` -- Warning framework |
| 299 | |
| 300 | |
| 301 | .. cmdoption:: -x |
| 302 | |
| 303 | Skip the first line of the source, allowing use of non-Unix forms of |
| 304 | ``#!cmd``. This is intended for a DOS specific hack only. |
| 305 | |
| 306 | .. warning:: The line numbers in error messages will be off by one! |
| 307 | |
| 308 | |
| 309 | .. cmdoption:: -3 |
| 310 | |
Georg Brandl | 87983f2 | 2007-12-01 23:12:45 +0000 | [diff] [blame^] | 311 | Warn about Python 3.x incompatibilities. Among these are: |
| 312 | |
| 313 | * :meth:`dict.has_key` |
| 314 | * :func:`apply` |
| 315 | * :func:`callable` |
| 316 | * :func:`coerce` |
| 317 | * :func:`execfile` |
| 318 | * :func:`reduce` |
| 319 | * :func:`reload` |
Georg Brandl | 59d121a | 2007-10-20 18:08:14 +0000 | [diff] [blame] | 320 | |
| 321 | .. versionadded:: 2.6 |
| 322 | |
| 323 | |
Georg Brandl | 59d121a | 2007-10-20 18:08:14 +0000 | [diff] [blame] | 324 | |
Georg Brandl | 87983f2 | 2007-12-01 23:12:45 +0000 | [diff] [blame^] | 325 | .. _using-on-envvars: |
Georg Brandl | 59d121a | 2007-10-20 18:08:14 +0000 | [diff] [blame] | 326 | |
| 327 | Environment variables |
| 328 | --------------------- |
| 329 | |
| 330 | .. envvar:: PYTHONHOME |
| 331 | |
| 332 | Change the location of the standard Python libraries. By default, the |
| 333 | libraries are searched in :file:`{prefix}/lib/python<version>` and |
| 334 | :file:`{exec_prefix}/lib/python<version>`, where :file:`{prefix}` and |
| 335 | :file:`{exec_prefix}` are installation-dependent directories, both defaulting |
| 336 | to :file:`/usr/local`. |
| 337 | |
| 338 | When :envvar:`PYTHONHOME` is set to a single directory, its value replaces |
| 339 | both :file:`{prefix}` and :file:`{exec_prefix}`. To specify different values |
| 340 | for these, set :envvar:`PYTHONHOME` to :file:`{prefix}:{exec_prefix}``. |
| 341 | |
| 342 | |
| 343 | .. envvar:: PYTHONPATH |
| 344 | |
| 345 | Augments the default search path for module files. The format is the same as |
| 346 | the shell's :envvar:`PATH`: one or more directory pathnames separated by |
| 347 | colons. Non-existent directories are silently ignored. |
| 348 | |
| 349 | The default search path is installation dependent, but generally begins with |
| 350 | :file:`{prefix}/lib/python<version>`` (see :envvar:`PYTHONHOME` above). It |
| 351 | is *always* appended to :envvar:`PYTHONPATH`. |
| 352 | |
| 353 | If a script argument is given, the directory containing the script is |
| 354 | inserted in the path in front of :envvar:`PYTHONPATH`. The search path can |
| 355 | be manipulated from within a Python program as the variable :data:`sys.path`. |
| 356 | |
| 357 | |
| 358 | .. envvar:: PYTHONSTARTUP |
| 359 | |
| 360 | If this is the name of a readable file, the Python commands in that file are |
| 361 | executed before the first prompt is displayed in interactive mode. The file |
Georg Brandl | a739503 | 2007-10-21 12:15:05 +0000 | [diff] [blame] | 362 | is executed in the same namespace where interactive commands are executed so |
Georg Brandl | 59d121a | 2007-10-20 18:08:14 +0000 | [diff] [blame] | 363 | that objects defined or imported in it can be used without qualification in |
| 364 | the interactive session. You can also change the prompts :data:`sys.ps1` and |
| 365 | :data:`sys.ps2` in this file. |
| 366 | |
| 367 | |
| 368 | .. envvar:: PYTHONY2K |
| 369 | |
| 370 | Set this to a non-empty string to cause the :mod:`time` module to require |
| 371 | dates specified as strings to include 4-digit years, otherwise 2-digit years |
| 372 | are converted based on rules described in the :mod:`time` module |
| 373 | documentation. |
| 374 | |
| 375 | |
| 376 | .. envvar:: PYTHONOPTIMIZE |
| 377 | |
| 378 | If this is set to a non-empty string it is equivalent to specifying the |
| 379 | :option:`-O` option. If set to an integer, it is equivalent to specifying |
| 380 | :option:`-O` multiple times. |
| 381 | |
| 382 | |
| 383 | .. envvar:: PYTHONDEBUG |
| 384 | |
| 385 | If this is set to a non-empty string it is equivalent to specifying the |
| 386 | :option:`-d` option. If set to an integer, it is equivalent to specifying |
| 387 | :option:`-d` multiple times. |
| 388 | |
| 389 | |
| 390 | .. envvar:: PYTHONINSPECT |
| 391 | |
| 392 | If this is set to a non-empty string it is equivalent to specifying the |
| 393 | :option:`-i` option. |
| 394 | |
| 395 | |
| 396 | .. envvar:: PYTHONUNBUFFERED |
| 397 | |
| 398 | If this is set to a non-empty string it is equivalent to specifying the |
| 399 | :option:`-u` option. |
| 400 | |
| 401 | |
| 402 | .. envvar:: PYTHONVERBOSE |
| 403 | |
| 404 | If this is set to a non-empty string it is equivalent to specifying the |
| 405 | :option:`-v` option. If set to an integer, it is equivalent to specifying |
| 406 | :option:`-v` multiple times. |
| 407 | |
| 408 | |
| 409 | .. envvar:: PYTHONCASEOK |
| 410 | |
| 411 | If this is set, Python ignores case in :keyword:`import` statements. This |
| 412 | only works on Windows. |
| 413 | |