MAN page from CentOS 7 python-2.7.5-88.el7.x86_64.rpm


Section: Misc. Reference Manual Pages (1)



python - an interpreted, interactive, object-oriented programming language 


python[-B][-d][-E][-h][-i][-m module-name]





Python is an interpreted, interactive, object-oriented programminglanguage that combines remarkable power with very clear syntax.For an introduction to programming in Python you are referred to thePython Tutorial.The Python Library Reference documents built-in and standard types,constants, functions and modules.Finally, the Python Reference Manual describes the syntax andsemantics of the core language in (perhaps too) much detail.(These documents may be located via theINTERNET RESOURCESbelow; they may be installed on your system as well.)

Python's basic power can be extended with your own modules written inC or C++.On most systems such modules may be dynamically loaded.Python is also adaptable as an extension language for existingapplications.See the internal documentation for hints.

Documentation for installed Python modules and packages can be viewed by running the pydocprogram.  


Don't[co]files on import. See also PYTHONDONTWRITEBYTECODE.
-c command
Specify the command to execute (see next section).This terminates the option list (following options are passed asarguments to the command).
Turn on parser debugging output (for wizards only, depending oncompilation options).
Ignore environment variables like PYTHONPATH and PYTHONHOME that modifythe behavior of the interpreter.
-h , -? , --help
Prints the usage for the interpreter executable and exits.
When a script is passed as first argument or the -c option isused, enter interactive mode after executing the script or thecommand. It does not read the $PYTHONSTARTUP file. This can beuseful to inspect global variables or a stack trace when a scriptraises an exception.
-m module-name
Searches sys.path for the named module and runs the corresponding .py file as a script.
Turn on basic optimizations. This changes the filename extension forcompiled (bytecode) files from.pycto .pyo. Given twice, causes docstrings to be discarded.
Discard docstrings in addition to the -O optimizations.
Turn on "hash randomization", so that the hash() values of str, bytes anddatetime objects are "salted" with an unpredictable pseudo-random value.Although they remain constant within an individual Python process, they arenot predictable between repeated invocations of Python.
This is intended to provide protection against a denial of servicecaused by carefully-chosen inputs that exploit the worst case performanceof a dict construction, O(n^2) complexity. See details.
-Q argument
Division control; see PEP 238. The argument must be one of "old" (thedefault, int/int and long/long return an int or long), "new" (newdivision semantics, i.e. int/int and long/long returns a float),"warn" (old division semantics with a warning for int/int andlong/long), or "warnall" (old division semantics with a warning forall use of the division operator). For a use of "warnall", see theTools/scripts/ script.
Don't add user site directory to sys.path.
Disable the import of the modulesiteand the site-dependent manipulations ofsys.paththat it entails.
Issue a warning when a source file mixes tabs and spaces forindentation in a way that makes it depend on the worth of a tabexpressed in spaces. Issue an error when the option is given twice.
Force stdin, stdout and stderr to be totally unbuffered. On systemswhere it matters, also put stdin, stdout and stderr in binary mode.Note that there is internal buffering in xreadlines(), readlines() andfile-object iterators ("for line in sys.stdin") which is notinfluenced by this option. To work around this, you will want to use"sys.stdin.readline()" inside a "while 1:" loop.
Print a message each time a module is initialized, showing the place(filename or built-in module) from which it is loaded. When giventwice, print a message for each file that is checked for when searching for a module. Also provides information on module cleanupat exit.
-V , --version
Prints the Python version number of the executable and exits.
-W argument
Warning control. Python sometimes prints warning message tosys.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 itoccurs. This option controls how often warnings are printed.Multiple-Woptions may be given; when a warning matches more than oneoption, the action for the last matching option is performed.Invalid-Woptions are ignored (a warning message is printed about invalidoptions when the first warning is issued). Warnings can also becontrolled from within a Python program using thewarningsmodule.

The simplest form ofargumentis one of the followingactionstrings (or a unique abbreviation):ignoreto ignore all warnings;defaultto explicitly request the default behavior (printing each warning onceper source line);allto print a warning each time it occurs (this may generate manymessages if a warning is triggered repeatedly for the same sourceline, such as inside a loop);moduleto print each warning only the first time it occurs in eachmodule;onceto print each warning only the first time it occurs in the program; orerrorto raise an exception instead of printing a warning message.

The full form ofargumentisaction:message:category:module:line.Here,actionis as explained above but only applies to messages that match theremaining fields. Empty fields match all values; trailing emptyfields may be omitted. Themessagefield matches the start of the warning message printed; this match iscase-insensitive. Thecategoryfield matches the warning category. This must be a class name; thematch test whether the actual warning category of the message is asubclass of the specified warning category. The full class name mustbe given. Themodulefield matches the (fully-qualified) module name; this match iscase-sensitive. Thelinefield matches the line number, where zero matches all line numbers andis thus equivalent to an omitted line number.

Skip the first line of the source. This is intended for a DOSspecific hack only. Warning: the line numbers in error messages willbe off by one!
Warn about Python 3.x incompatibilities that 2to3 cannot trivially fix.


The interpreter interface resembles that of the UNIX shell: whencalled with standard input connected to a tty device, it prompts forcommands and executes them until an EOF is read; when called with afile name argument or with a file as standard input, it reads andexecutes ascriptfrom that file;when called with-ccommand,it executes the Python statement(s) given ascommand.Herecommandmay contain multiple statements separated by newlines.Leading whitespace is significant in Python statements!In non-interactive mode, the entire input is parsed before it isexecuted.

If available, the script name and additional arguments thereafter arepassed to the script in the Python variablesys.argv ,which is a list of strings (you must firstimport systo be able to access it).If no script name is given,sys.argv[0]is an empty string; if-cis used,sys.argv[0]contains the string'-c'.Note that options interpreted by the Python interpreter itselfare not placed insys.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 tosys.ps1orsys.ps2.The interpreter quits when it reads an EOF at a prompt.When an unhandled exception occurs, a stack trace is printed andcontrol returns to the primary prompt; in non-interactive mode, theinterpreter exits after printing the stack trace.The interrupt signal raises theKeyboardInterruptexception; other UNIX signals are not caught (except that SIGPIPE issometimes ignored, in favor of theIOErrorexception). Error messages are written to stderr. 


These are subject to difference depending on local installationconventions; ${prefix} and ${exec_prefix} are installation-dependentand should be interpreted as for GNU software; they may be the same.The default for both is /usr/local.
Recommended location of the interpreter.


Recommended locations of the directories containing the standardmodules.


Recommended locations of the directories containing the include filesneeded for developing Python extensions and embedding theinterpreter.
User-specific initialization file loaded by the user module;not used by default or by most applications.


Change the location of the standard Python libraries. By default, thelibraries are searched in ${prefix}/lib/python<version> and${exec_prefix}/lib/python<version>, where ${prefix} and ${exec_prefix}are installation-dependent directories, both defaulting to/usr/local. When $PYTHONHOME is set to a single directory, its valuereplaces both ${prefix} and ${exec_prefix}. To specify different valuesfor these, set $PYTHONHOME to ${prefix}:${exec_prefix}.
Augments the default search path for module files.The format is the same as the shell's $PATH: one or more directorypathnames separated by colons.Non-existent directories are silently ignored.The default search path is installation dependent, but generallybegins with ${prefix}/lib/python<version> (see PYTHONHOME above).The default search path is always appended to $PYTHONPATH.If a script argument is given, the directory containing the script isinserted in the path in front of $PYTHONPATH.The search path can be manipulated from within a Python program as thevariablesys.path .
If this is the name of a readable file, the Python commands in thatfile are executed before the first prompt is displayed in interactivemode.The file is executed in the same name space where interactive commandsare executed so that objects defined or imported in it can be usedwithout qualification in the interactive session.You can also change the promptssys.ps1andsys.ps2in this file.
Set this to a non-empty string to cause the time module torequire dates specified as strings to include 4-digit years, otherwise2-digit years are converted based on rules described in the timemodule documentation.
If this is set to a non-empty string it is equivalent to specifyingthe -O option. If set to an integer, it is equivalent tospecifying -O multiple times.
If this is set to a non-empty string it is equivalent to specifyingthe -d option. If set to an integer, it is equivalent tospecifying -d multiple times.
If this is set to a non-empty string it is equivalent to specifyingthe -B option (don't try to[co]files).
If this is set to a non-empty string it is equivalent to specifyingthe -i option.
If this is set before running the interpreter, it overrides the encoding usedfor stdin/stdout/stderr, in the syntaxencodingname:errorhandlerTheerrorhandlerpart is optional and has the same meaning as in str.encode. For stderr, theerrorhandler
 part is ignored; the handler will always be 'backslashreplace'.
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).
If this is set to a non-empty string it is equivalent to specifyingthe -u option.
If this is set to a non-empty string it is equivalent to specifyingthe -v option. If set to an integer, it is equivalent tospecifying -v multiple times.
If this is set to a comma-separated string it is equivalent tospecifying the -W option for each separate value.
If this variable is set to "random", the effect is the same as specifyingthe -R option: 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 forgenerating the hash() of the types covered by the hash randomization. Itspurpose is to allow repeatable hashing, such as for selftests for theinterpreter itself, or to allow a cluster of python processes to share hashvalues.

The integer must be a decimal number in the range [0,4294967295]. Specifyingthe value 0 will lead to the same hash values as when hash randomization isdisabled.



The Python Software Foundation: 


Main website:
Developer resources:
Module repository:
Newsgroups: comp.lang.python, comp.lang.python.announce 


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 aDISCLAIMER OF ALL WARRANTIES.




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