# phpman > man > python2.7(1) [PYTHON(1)](https://www.chedong.com/phpMan.php/man/PYTHON/1/markdown) General Commands Manual [PYTHON(1)](https://www.chedong.com/phpMan.php/man/PYTHON/1/markdown) ## NAME python - an interpreted, interactive, object-oriented programming language ## SYNOPSIS **python** [ **-B** ] [ **-d** ] [ **-E** ] [ **-h** ] [ **-i** ] [ **-m** _module-name_ ] [ **-O** ] [ **-OO** ] [ **-R** ] [ **-Q** _argument_ ] [ **-s** ] [ **-S** ] [ **-t** ] [ **-u** ] [ **-v** ] [ **-V** ] [ **-W** _argument_ ] [ **-x** ] [ **-3** ] [ **-?** ] [ **-c** _command_ | _script_ | - ] [ _arguments_ ] ## DESCRIPTION Python is an interpreted, interactive, object-oriented programming language that combines re‐ markable power with very clear syntax. For an introduction to programming in Python, see the Python Tutorial. The Python Library Reference documents built-in and standard types, con‐ stants, functions and modules. Finally, the Python Reference Manual describes the syntax and semantics of the core language in (perhaps too) much detail. (These documents may be located via the **INTERNET** **RESOURCES** below; they may be installed on your system as well.) Python's basic power can be extended with your own modules written in C or C++. On most sys‐ tems such modules may be dynamically loaded. Python is also adaptable as an extension lan‐ guage for existing applications. See the internal documentation for hints. Documentation for installed Python modules and packages can be viewed by running the **pydoc** program. ## COMMAND LINE OPTIONS ### -B ### -c Specify the command to execute (see next section). This terminates the option list (following options are passed as arguments to the command). ### -d ### -E of the interpreter. ### -h , -? , --help Prints the usage for the interpreter executable and exits. ### -i -c mode after executing the script or the command. It does not read the $PYTHONSTARTUP file. This can be useful to inspect global variables or a stack trace when a script raises an exception. ### -m Searches _sys.path_ for the named module and runs the corresponding _.py_ file as a script. ### -O code) files from _.pyc_ to _.pyo_. Given twice, causes docstrings to be discarded. ### -OO -O ### -R jects are "salted" with an unpredictable pseudo-random value. Although they remain constant within an individual Python process, they are not predictable between re‐ peated invocations of Python. This is intended to provide protection against a denial of service caused by care‐ fully-chosen inputs that exploit the worst case performance of a dict construction, O(n^2) complexity. See for de‐ tails. ### -Q Division control; see PEP 238. The argument must be one of "old" (the default, int/int and long/long return an int or long), "new" (new division semantics, i.e. int/int and long/long returns a float), "warn" (old division semantics with a warning for int/int and long/long), or "warnall" (old division semantics with a warning for all use of the division operator). For a use of "warnall", see the Tools/scripts/fix‐ div.py script. ### -s ### -S that it entails. ### -t makes it depend on the worth of a tab expressed in spaces. Issue an error when the option is given twice. ### -u also put stdin, stdout and stderr in binary mode. Note that there is internal buffer‐ ing in xreadlines(), readlines() and file-object iterators ("for line in sys.stdin") which is not influenced by this option. To work around this, you will want to use "sys.stdin.readline()" inside a "while 1:" loop. ### -v built-in module) from which it is loaded. When given twice, print a message for each file that is checked for when searching for a module. Also provides information on module cleanup at exit. ### -V , --version Prints the Python version number of the executable and exits. ### -W Warning control. Python sometimes prints warning message to _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 con‐ trols how often warnings are printed. Multiple **-W** options may be given; when a warn‐ ing matches more than one option, the action for the last matching option is per‐ formed. Invalid **-W** options are ignored (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 _warnings_ module. The simplest form of _argument_ is one of the following _action_ strings (or a unique ab‐ breviation): **ignore** to ignore all warnings; **default** to explicitly request the default behavior (printing each warning once per source line); **all** to 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** to print each warning only the first time it occurs in each module; **once** to print each warning only the first time it occurs in the program; or **error** to 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. ### -x Warning: the line numbers in error messages will be off by one! ### -3 ## INTERPRETER INTERFACE The interpreter interface resembles that of the UNIX shell: when called with standard input connected to a tty device, it prompts for commands and executes them until an EOF 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 **-c** _command_, it executes the Python statement(s) given as _command_. Here _command_ may contain multiple statements separated by newlines. Lead‐ ing whitespace is significant in Python statements! In non-interactive mode, the entire in‐ put is parsed before it is executed. If available, the script name and additional arguments thereafter are passed to the script in the Python variable _sys.argv_, which is a list of strings (you must first _import_ _sys_ to be able to access it). If no script name is given, _sys.argv[0]_ is an empty string; if **-c** is used, _sys.argv[0]_ contains the string _'-c'._ Note that options interpreted by the Python in‐ terpreter itself are not placed in _sys.argv_. In interactive mode, the primary prompt is `>>>'; the second prompt (which appears when a command is not complete) is `...'. The prompts can be changed by assignment to _sys.ps1_ or _sys.ps2_. The interpreter quits when it reads an EOF at a prompt. When an unhandled excep‐ tion occurs, a stack trace is printed and control returns to the primary prompt; in non-in‐ teractive mode, the interpreter exits after printing the stack trace. The interrupt signal raises the _KeyboardInterrupt_ exception; other UNIX signals are not caught (except that SIG‐ PIPE is sometimes ignored, in favor of the _IOError_ exception). Error messages are written to stderr. ## FILES AND DIRECTORIES These are subject to difference depending on local installation conventions; ${prefix} and ${exec_prefix} are installation-dependent and should be interpreted as for GNU software; they may be the same. On Debian GNU/{Hurd,Linux} the default for both is _/usr_. _${exec_prefix}/bin/python_ Recommended location of the interpreter. _${prefix}/lib/python_ _${exec_prefix}/lib/python_ Recommended locations of the directories containing the standard modules. _${prefix}/include/python_ _${exec_prefix}/include/python_ Recommended locations of the directories containing the include files needed for de‐ veloping Python extensions and embedding the interpreter. _~/.pythonrc.py_ User-specific initialization file loaded by the _user_ module; not used by default or by most applications. ## ENVIRONMENT VARIABLES PYTHONHOME Change the location of the standard Python libraries. By default, the libraries are searched in ${prefix}/lib/python and ${exec_prefix}/lib/python, where ${prefix} and ${exec_prefix} are installation-dependent directories, both de‐ faulting to _/usr/local_. When $PYTHONHOME is set to a single directory, its value re‐ places both ${prefix} and ${exec_prefix}. To specify different values for these, set $PYTHONHOME to ${prefix}:${exec_prefix}. PYTHONPATH Augments the default search path for module files. The format is the same as the shell's $PATH: one or more directory pathnames separated by colons. Non-existent di‐ rectories are silently ignored. The default search path is installation dependent, but generally begins with ${prefix}/lib/python (see PYTHONHOME above). The default search path is always appended to $PYTHONPATH. If a script argument is given, the directory containing the script is inserted in the path in front of $PYTHONPATH. The search path can be manipulated from within a Python program as the variable _sys.path_. 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 name space where interactive commands are executed so that objects defined or im‐ ported in it can be used without qualification in the interactive session. You can also change the prompts _sys.ps1_ and _sys.ps2_ in this file. PYTHONY2K Set this to a non-empty string to cause the _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 _time_ module documentation. PYTHONOPTIMIZE If this is set to a non-empty string it is equivalent to specifying the **-O** option. If set to an integer, it is equivalent to specifying **-O** multiple times. PYTHONDEBUG If this is set to a non-empty string it is equivalent to specifying the **-d** option. If set to an integer, it is equivalent to specifying **-d** multiple times. PYTHONDONTWRITEBYTECODE If this is set to a non-empty string it is equivalent to specifying the **-B** option (don't try to write _.py[co]_ files). PYTHONINSPECT If this is set to a non-empty string it is equivalent to specifying the **-i** option. PYTHONIOENCODING If this is set before running the interpreter, it overrides the encoding used for stdin/stdout/stderr, in the syntax _encodingname_**:**_errorhandler_ The _errorhandler_ part is optional and has the same meaning as in str.encode. For stderr, the _errorhandler_ part is ignored; the handler will always be ´backslashreplace´. PYTHONNOUSERSITE If this is set to a non-empty string it is equivalent to specifying the **-s** option (Don't add the user site directory to sys.path). PYTHONUNBUFFERED If this is set to a non-empty string it is equivalent to specifying the **-u** option. PYTHONVERBOSE If this is set to a non-empty string it is equivalent to specifying the **-v** option. If set to an integer, it is equivalent to specifying **-v** multiple times. PYTHONWARNINGS If this is set to a comma-separated string it is equivalent to specifying the **-W** op‐ tion for each separate value. PYTHONHASHSEED If this variable is set to "random", the effect is the same as specifying the **-R** op‐ tion: a random value is used to seed the hashes of str, bytes and datetime objects. If PYTHONHASHSEED is set to an integer value, it is used as a fixed seed for generat‐ ing the hash() of the types covered by the hash randomization. Its purpose is to al‐ low repeatable hashing, such as for selftests for the interpreter itself, or to allow a cluster of python processes to share hash values. The integer must be a decimal number in the range [0,4294967295]. Specifying the value 0 will lead to the same hash values as when hash randomization is disabled. ## AUTHOR The Python Software Foundation: ## INTERNET RESOURCES Main website: Documentation: file:///usr/share/doc/python2.7/html/index.html (python-doc package) or Developer resources: Downloads: Module repository: Newsgroups: comp.lang.python, comp.lang.python.announce ## LICENSING Python is distributed under an Open Source license. See the file "LICENSE" in the Python source distribution for information on terms & conditions for accessing and otherwise using Python and for a DISCLAIMER OF ALL WARRANTIES. [PYTHON(1)](https://www.chedong.com/phpMan.php/man/PYTHON/1/markdown)