1PYTHON(1) General Commands Manual PYTHON(1)
2
6 python - an interpreted, interactive, object-oriented programming lan‐
7 guage
8
10 python [ -B ] [ -b ] [ -d ] [ -E ] [ -h ] [ -i ] [ -I ]
11 [ -m module-name ] [ -q ] [ -O ] [ -OO ] [ -s ] [ -S ] [ -u ]
12 [ -v ] [ -V ] [ -W argument ] [ -x ] [ [ -X option ] -? ]
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, see the Python Tutorial. The
19 Python Library Reference documents built-in and standard types, con‐
20 stants, functions and modules. Finally, the Python Reference Manual
21 describes the syntax and semantics of the core language in (perhaps
22 too) much detail. (These documents may be located via the INTERNET
23 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 .pyc files on import. See also PYTHONDONTWRITEBYTE‐
35 CODE.
36 -b Issue warnings about str(bytes_instance), str(bytear‐
38 ray_instance) and comparing bytes/bytearray with str. (-bb:
39 issue errors)
40 -c command
42 Specify the command to execute (see next section). This termi‐
43 nates the option list (following options are passed as arguments
44 to the command).
45 -d Turn on parser debugging output (for wizards only, depending on
47 compilation options).
48 -E Ignore environment variables like PYTHONPATH and PYTHONHOME that
50 modify the behavior of the interpreter.
51 -h , -? , --help
53 Prints the usage for the interpreter executable and exits.
54 -i When a script is passed as first argument or the -c option is
56 used, enter interactive mode after executing the script or the
57 command. It does not read the $PYTHONSTARTUP file. This can be
58 useful to inspect global variables or a stack trace when a
59 script raises an exception.
60 -I Run Python in isolated mode. This also implies -E and -s. In
62 isolated mode sys.path contains neither the script's directory
63 nor the user's site-packages directory. All PYTHON* environment
64 variables are ignored, too. Further restrictions may be imposed
65 to prevent the user from injecting malicious code.
66 -m module-name
68 Searches sys.path for the named module and runs the correspond‐
69 ing .py file as a script.
70 -O Turn on basic optimizations. Given twice, causes docstrings to
72 be discarded.
73 -OO Discard docstrings in addition to the -O optimizations.
75 -q Do not print the version and copyright messages. These messages
77 are also suppressed in non-interactive mode.
78 -s Don't add user site directory to sys.path.
80 -S Disable the import of the module site and the site-dependent
82 manipulations of sys.path that it entails. Also disable these
83 manipulations if site is explicitly imported later.
84 -u Force the binary I/O layers of stdout and stderr to be
86 unbuffered. stdin is always buffered. The text I/O layer will
87 still be line-buffered.
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 option
137 Set implementation specific option.
138 -x Skip the first line of the source. This is intended for a DOS
140 specific hack only. Warning: the line numbers in error messages
141 will be off by one!
142
144 The interpreter interface resembles that of the UNIX shell: when called
145 with standard input connected to a tty device, it prompts for commands
146 and executes them until an EOF is read; when called with a file name
147 argument or with a file as standard input, it reads and executes a
148 script from that file; when called with -c command, it executes the
149 Python statement(s) given as command. Here command may contain multi‐
150 ple statements separated by newlines. Leading whitespace is signifi‐
151 cant in Python statements! In non-interactive mode, the entire input
152 is parsed before it is executed.
153 If available, the script name and additional arguments thereafter are
155 passed to the script in the Python variable sys.argv, which is a list
156 of strings (you must first import sys to be able to access it). If no
157 script name is given, sys.argv[0] is an empty string; if -c is used,
158 sys.argv[0] contains the string '-c'. Note that options interpreted by
159 the Python interpreter itself are not placed in sys.argv.
160 In interactive mode, the primary prompt is `>>>'; the second prompt
162 (which appears when a command is not complete) is `...'. The prompts
163 can be changed by assignment to sys.ps1 or sys.ps2. The interpreter
164 quits when it reads an EOF at a prompt. When an unhandled exception
165 occurs, a stack trace is printed and control returns to the primary
166 prompt; in non-interactive mode, the interpreter exits after printing
167 the stack trace. The interrupt signal raises the KeyboardInterrupt
168 exception; other UNIX signals are not caught (except that SIGPIPE is
169 sometimes ignored, in favor of the IOError exception). Error messages
170 are written to stderr.
171
173 These are subject to difference depending on local installation conven‐
174 tions; ${prefix} and ${exec_prefix} are installation-dependent and
175 should be interpreted as for GNU software; they may be the same. The
176 default for both is /usr/local.
177 ${exec_prefix}/bin/python
179 Recommended location of the interpreter.
180 ${prefix}/lib/python<version>
182 ${exec_prefix}/lib/python<version>
183 Recommended locations of the directories containing the standard
184 modules.
185 ${prefix}/include/python<version>
187 ${exec_prefix}/include/python<version>
188 Recommended locations of the directories containing the include
189 files needed for developing Python extensions and embedding the
190 interpreter.
191
193 PYTHONHOME
194 Change the location of the standard Python libraries. By
195 default, the libraries are searched in ${prefix}/lib/python<ver‐
196 sion> and ${exec_prefix}/lib/python<version>, where ${prefix}
197 and ${exec_prefix} are installation-dependent directories, both
198 defaulting to /usr/local. When $PYTHONHOME is set to a single
199 directory, its value replaces both ${prefix} and ${exec_prefix}.
200 To specify different values for these, set $PYTHONHOME to ${pre‐
201 fix}:${exec_prefix}.
202 PYTHONPATH
204 Augments the default search path for module files. The format
205 is the same as the shell's $PATH: one or more directory path‐
206 names separated by colons. Non-existent directories are
207 silently ignored. The default search path is installation
208 dependent, but generally begins with ${prefix}/lib/python<ver‐
209 sion> (see PYTHONHOME above). The default search path is always
210 appended to $PYTHONPATH. If a script argument is given, the
211 directory containing the script is inserted in the path in front
212 of $PYTHONPATH. The search path can be manipulated from within
213 a Python program as the variable sys.path.
214 PYTHONSTARTUP
216 If this is the name of a readable file, the Python commands in
217 that file are executed before the first prompt is displayed in
218 interactive mode. The file is executed in the same name space
219 where interactive commands are executed so that objects defined
220 or imported in it can be used without qualification in the
221 interactive session. You can also change the prompts sys.ps1
222 and sys.ps2 in this file.
223 PYTHONOPTIMIZE
225 If this is set to a non-empty string it is equivalent to speci‐
226 fying the -O option. If set to an integer, it is equivalent to
227 specifying -O multiple times.
228 PYTHONDEBUG
230 If this is set to a non-empty string it is equivalent to speci‐
231 fying the -d option. If set to an integer, it is equivalent to
232 specifying -d multiple times.
233 PYTHONDONTWRITEBYTECODE
235 If this is set to a non-empty string it is equivalent to speci‐
236 fying the -B option (don't try to write .pyc files).
237 PYTHONINSPECT
239 If this is set to a non-empty string it is equivalent to speci‐
240 fying the -i option.
241 PYTHONIOENCODING
243 If this is set before running the interpreter, it overrides the
244 encoding used for stdin/stdout/stderr, in the syntax encoding‐
245 name:errorhandler The errorhandler part is optional and has the
246 same meaning as in str.encode. For stderr, the errorhandler
247 part is ignored; the handler will always be ´backslashreplace´.
248 PYTHONNOUSERSITE
250 If this is set to a non-empty string it is equivalent to speci‐
251 fying the -s option (Don't add the user site directory to
252 sys.path).
253 PYTHONUNBUFFERED
255 If this is set to a non-empty string it is equivalent to speci‐
256 fying the -u option.
257 PYTHONVERBOSE
259 If this is set to a non-empty string it is equivalent to speci‐
260 fying the -v option. If set to an integer, it is equivalent to
261 specifying -v multiple times.
262 PYTHONWARNINGS
264 If this is set to a comma-separated string it is equivalent to
265 specifying the -W option for each separate value.
266 PYTHONHASHSEED
268 If this variable is set to "random", a random value is used to
269 seed the hashes of str, bytes and datetime objects.
270 If PYTHONHASHSEED is set to an integer value, it is used as a
272 fixed seed for generating the hash() of the types covered by the
273 hash randomization. Its purpose is to allow repeatable hashing,
274 such as for selftests for the interpreter itself, or to allow a
275 cluster of python processes to share hash values.
276 The integer must be a decimal number in the range
278 [0,4294967295]. Specifying the value 0 will disable hash ran‐
279 domization.
280
282 The Python Software Foundation: https://www.python.org/psf/
283
285 Main website: https://www.python.org/
286 Documentation: https://docs.python.org/
287 Developer resources: https://docs.python.org/devguide/
288 Downloads: https://www.python.org/downloads/
289 Module repository: https://pypi.python.org/
290 Newsgroups: comp.lang.python, comp.lang.python.announce
291
293 Python is distributed under an Open Source license. See the file
294 "LICENSE" in the Python source distribution for information on terms &
295 conditions for accessing and otherwise using Python and for a DIS‐
296 CLAIMER OF ALL WARRANTIES.
297 PYTHON(1)