1PYTHON(1) General Commands Manual PYTHON(1)
2
6 python - an interpreted, interactive, object-oriented programming lan‐
7 guage
8
10 python [ -B ] [ -d ] [ -E ] [ -h ] [ -i ] [ -m module-name ]
11 [ -O ] [ -O0 ] [ -Q argument ] [ -s ] [ -S ] [ -u ]
12 [ -v ] [ -V ] [ -W argument ] [ -x ] [ -? ]
13 [ -c command | script | - ] [ arguments ]
14
16 Python is an interpreted, interactive, object-oriented programming lan‐
17 guage that combines remarkable power with very clear syntax. For an
18 introduction to programming in Python you are referred to the Python
19 Tutorial. The Python Library Reference documents built-in and standard
20 types, constants, functions and modules. Finally, the Python Reference
21 Manual describes the syntax and semantics of the core language in (per‐
22 haps too) much detail. (These documents may be located via the INTER‐
23 NET RESOURCES below; they may be installed on your system as well.)
24 Python's basic power can be extended with your own modules written in C
26 or C++. On most systems such modules may be dynamically loaded.
27 Python is also adaptable as an extension language for existing applica‐
28 tions. See the internal documentation for hints.
29 Documentation for installed Python modules and packages can be viewed
31 by running the pydoc program.
32
34 -B Don't write .py[co] files on import. See also PYTHONDONTWRITE‐
35 BYTECODE.
36 -c command
38 Specify the command to execute (see next section). This termi‐
39 nates the option list (following options are passed as arguments
40 to the command).
41 -d Turn on parser debugging output (for wizards only, depending on
43 compilation options).
44 -E Ignore environment variables like PYTHONPATH and PYTHONHOME that
46 modify the behavior of the interpreter.
47 -h , -? , --help
49 Prints the usage for the interpreter executable and exits.
50 -i When a script is passed as first argument or the -c option is
52 used, enter interactive mode after executing the script or the
53 command. It does not read the $PYTHONSTARTUP file. This can be
54 useful to inspect global variables or a stack trace when a
55 script raises an exception.
56 -m module-name
58 Searches sys.path for the named module and runs the correspond‐
59 ing .py file as a script.
60 -O Turn on basic optimizations. This changes the filename exten‐
62 sion for compiled (bytecode) files from .pyc to .pyo. Given
63 twice, causes docstrings to be discarded.
64 -O0 Discard docstrings in addition to the -O optimizations.
66 -Q argument
68 Division control; see PEP 238. The argument must be one of
69 "old" (the default, int/int and long/long return an int or
70 long), "new" (new division semantics, i.e. int/int and long/long
71 returns a float), "warn" (old division semantics with a warning
72 for int/int and long/long), or "warnall" (old division semantics
73 with a warning for all use of the division operator). For a use
74 of "warnall", see the Tools/scripts/fixdiv.py script.
75 -s Don't add user site directory to sys.path.
77 -S Disable the import of the module site and the site-dependent
79 manipulations of sys.path that it entails.
80 -u Force stdin, stdout and stderr to be totally unbuffered. On
82 systems where it matters, also put stdin, stdout and stderr in
83 binary mode. Note that there is internal buffering in read‐
84 lines() and file-object iterators ("for line in sys.stdin")
85 which is not influenced by this option. To work around this,
86 you will want to use "sys.stdin.readline()" inside a "while 1:"
87 loop.
88 -v Print a message each time a module is initialized, showing the
90 place (filename or built-in module) from which it is loaded.
91 When given twice, print a message for each file that is checked
92 for when searching for a module. Also provides information on
93 module cleanup at exit.
94 -V , --version
96 Prints the Python version number of the executable and exits.
97 -W argument
99 Warning control. Python sometimes prints warning message to
100 sys.stderr. A typical warning message has the following form:
101 file:line: category: message. By default, each warning is
102 printed once for each source line where it occurs. This option
103 controls how often warnings are printed. Multiple -W options
104 may be given; when a warning matches more than one option, the
105 action for the last matching option is performed. Invalid -W
106 options are ignored (a warning message is printed about invalid
107 options when the first warning is issued). Warnings can also be
108 controlled from within a Python program using the warnings mod‐
109 ule.
110 The simplest form of argument is one of the following action
112 strings (or a unique abbreviation): ignore to ignore all warn‐
113 ings; default to explicitly request the default behavior (print‐
114 ing each warning once per source line); all to print a warning
115 each time it occurs (this may generate many messages if a warn‐
116 ing is triggered repeatedly for the same source line, such as
117 inside a loop); module to print each warning only the first time
118 it occurs in each module; once to print each warning only the
119 first time it occurs in the program; or error to raise an excep‐
120 tion instead of printing a warning message.
121 The full form of argument is action:message:category:mod‐
123 ule:line. Here, action is as explained above but only applies
124 to messages that match the remaining fields. Empty fields match
125 all values; trailing empty fields may be omitted. The message
126 field matches the start of the warning message printed; this
127 match is case-insensitive. The category field matches the warn‐
128 ing category. This must be a class name; the match test whether
129 the actual warning category of the message is a subclass of the
130 specified warning category. The full class name must be given.
131 The module field matches the (fully-qualified) module name; this
132 match is case-sensitive. The line field matches the line num‐
133 ber, where zero matches all line numbers and is thus equivalent
134 to an omitted line number.
135 -x Skip the first line of the source. This is intended for a DOS
137 specific hack only. Warning: the line numbers in error messages
138 will be off by one!
139
141 The interpreter interface resembles that of the UNIX shell: when called
142 with standard input connected to a tty device, it prompts for commands
143 and executes them until an EOF is read; when called with a file name
144 argument or with a file as standard input, it reads and executes a
145 script from that file; when called with -c command, it executes the
146 Python statement(s) given as command. Here command may contain multi‐
147 ple statements separated by newlines. Leading whitespace is signifi‐
148 cant in Python statements! In non-interactive mode, the entire input
149 is parsed before it is executed.
150 If available, the script name and additional arguments thereafter are
152 passed to the script in the Python variable sys.argv , which is a list
153 of strings (you must first import sys to be able to access it). If no
154 script name is given, sys.argv[0] is an empty string; if -c is used,
155 sys.argv[0] contains the string '-c'. Note that options interpreted by
156 the Python interpreter itself are not placed in sys.argv.
157 In interactive mode, the primary prompt is `>>>'; the second prompt
159 (which appears when a command is not complete) is `...'. The prompts
160 can be changed by assignment to sys.ps1 or sys.ps2. The interpreter
161 quits when it reads an EOF at a prompt. When an unhandled exception
162 occurs, a stack trace is printed and control returns to the primary
163 prompt; in non-interactive mode, the interpreter exits after printing
164 the stack trace. The interrupt signal raises the KeyboardInterrupt
165 exception; other UNIX signals are not caught (except that SIGPIPE is
166 sometimes ignored, in favor of the IOError exception). Error messages
167 are written to stderr.
168
170 These are subject to difference depending on local installation conven‐
171 tions; ${prefix} and ${exec_prefix} are installation-dependent and
172 should be interpreted as for GNU software; they may be the same. The
173 default for both is /usr/local.
174 ${exec_prefix}/bin/python
176 Recommended location of the interpreter.
177 ${prefix}/lib/python<version>
179 ${exec_prefix}/lib/python<version>
180 Recommended locations of the directories containing the standard
181 modules.
182 ${prefix}/include/python<version>
184 ${exec_prefix}/include/python<version>
185 Recommended locations of the directories containing the include
186 files needed for developing Python extensions and embedding the
187 interpreter.
188
190 PYTHONHOME
191 Change the location of the standard Python libraries. By
192 default, the libraries are searched in ${prefix}/lib/python<ver‐
193 sion> and ${exec_prefix}/lib/python<version>, where ${prefix}
194 and ${exec_prefix} are installation-dependent directories, both
195 defaulting to /usr/local. When $PYTHONHOME is set to a single
196 directory, its value replaces both ${prefix} and ${exec_prefix}.
197 To specify different values for these, set $PYTHONHOME to ${pre‐
198 fix}:${exec_prefix}.
199 PYTHONPATH
201 Augments the default search path for module files. The format
202 is the same as the shell's $PATH: one or more directory path‐
203 names separated by colons. Non-existent directories are
204 silently ignored. The default search path is installation
205 dependent, but generally begins with ${prefix}/lib/python<ver‐
206 sion> (see PYTHONHOME above). The default search path is always
207 appended to $PYTHONPATH. If a script argument is given, the
208 directory containing the script is inserted in the path in front
209 of $PYTHONPATH. The search path can be manipulated from within
210 a Python program as the variable sys.path .
211 PYTHONSTARTUP
213 If this is the name of a readable file, the Python commands in
214 that file are executed before the first prompt is displayed in
215 interactive mode. The file is executed in the same name space
216 where interactive commands are executed so that objects defined
217 or imported in it can be used without qualification in the
218 interactive session. You can also change the prompts sys.ps1
219 and sys.ps2 in this file.
220 PYTHONY2K
222 Set this to a non-empty string to cause the time module to
223 require dates specified as strings to include 4-digit years,
224 otherwise 2-digit years are converted based on rules described
225 in the time module documentation.
226 PYTHONOPTIMIZE
228 If this is set to a non-empty string it is equivalent to speci‐
229 fying the -O option. If set to an integer, it is equivalent to
230 specifying -O multiple times.
231 PYTHONDEBUG
233 If this is set to a non-empty string it is equivalent to speci‐
234 fying the -d option. If set to an integer, it is equivalent to
235 specifying -d multiple times.
236 PYTHONDONTWRITEBYTECODE
238 If this is set to a non-empty string it is equivalent to speci‐
239 fying the -B option (don't try to write .py[co] files).
240 PYTHONINSPECT
242 If this is set to a non-empty string it is equivalent to speci‐
243 fying the -i option.
244 PYTHONNOUSERSITE
246 If this is set to a non-empty string it is equivalent to speci‐
247 fying the -s option (Don't add the user site directory to
248 sys.path).
249 PYTHONUNBUFFERED
251 If this is set to a non-empty string it is equivalent to speci‐
252 fying the -u option.
253 PYTHONVERBOSE
255 If this is set to a non-empty string it is equivalent to speci‐
256 fying the -v option. If set to an integer, it is equivalent to
257 specifying -v multiple times.
258
260 The Python Software Foundation: http://www.python.org/psf
261
263 Main website: http://www.python.org/
264 Documentation: http://docs.python.org/py3k/
265 Developer resources: http://www.python.org/dev/
266 Downloads: http://python.org/download/
267 Module repository: http://pypi.python.org/
268 Newsgroups: comp.lang.python, comp.lang.python.announce
269
271 Python is distributed under an Open Source license. See the file
272 "LICENSE" in the Python source distribution for information on terms &
273 conditions for accessing and otherwise using Python and for a DIS‐
274 CLAIMER OF ALL WARRANTIES.
275 $Date: 2010-01-31 10:17:23 -0600 (Sun, 31 Jan 2010) $ PYTHON(1)