.. module:: pydoc :synopsis: Documentation generator and online help system.
.. moduleauthor:: Ka-Ping Yee <ping@lfw.org>
.. sectionauthor:: Ka-Ping Yee <ping@lfw.org>
Source code: :source:`Lib/pydoc.py`
.. index:: single: documentation; generation single: documentation; online single: help; online
The :mod:`pydoc` module automatically generates documentation from Python modules. The documentation can be presented as pages of text on the console, served to a Web browser, or saved to HTML files.
For modules, classes, functions and methods, the displayed documentation is derived from the docstring (i.e. the :attr:`__doc__` attribute) of the object, and recursively of its documentable members. If there is no docstring, :mod:`pydoc` tries to obtain a description from the block of comment lines just above the definition of the class, function or method in the source file, or at the top of the module (see :func:`inspect.getcomments`).
The built-in function :func:`help` invokes the online help system in the interactive interpreter, which uses :mod:`pydoc` to generate its documentation as text on the console. The same text documentation can also be viewed from outside the Python interpreter by running :program:`pydoc` as a script at the operating system's command prompt. For example, running
pydoc sys
at a shell prompt will display documentation on the :mod:`sys` module, in a style similar to the manual pages shown by the Unix :program:`man` command. The argument to :program:`pydoc` can be the name of a function, module, or package, or a dotted reference to a class, method, or function within a module or module in a package. If the argument to :program:`pydoc` looks like a path (that is, it contains the path separator for your operating system, such as a slash in Unix), and refers to an existing Python source file, then documentation is produced for that file.
Note
In order to find objects and their documentation, :mod:`pydoc` imports the
module(s) to be documented. Therefore, any code on module level will be
executed on that occasion. Use an if __name__ == '__main__': guard to
only execute code when a file is invoked as a script and not just imported.
When printing output to the console, :program:`pydoc` attempts to paginate the output for easier reading. If the :envvar:`PAGER` environment variable is set, :program:`pydoc` will use its value as a pagination program.
Specifying a -w flag before the argument will cause HTML documentation
to be written out to a file in the current directory, instead of displaying text
on the console.
Specifying a -k flag before the argument will search the synopsis
lines of all available modules for the keyword given as the argument, again in a
manner similar to the Unix :program:`man` command. The synopsis line of a
module is the first line of its documentation string.
You can also use :program:`pydoc` to start an HTTP server on the local machine
that will serve documentation to visiting Web browsers. :program:`pydoc -p 1234`
will start a HTTP server on port 1234, allowing you to browse the
documentation at http://localhost:1234/ in your preferred Web browser.
Specifying 0 as the port number will select an arbitrary unused port.
:program:`pydoc -n <hostname>` will start the server listening at the given hostname. By default the hostname is 'localhost' but if you want the server to be reached from other machines, you may want to change the host name that the server responds to. During development this is especially useful if you want to run pydoc from within a container.
:program:`pydoc -b` will start the server and additionally open a web browser to a module index page. Each served page has a navigation bar at the top where you can Get help on an individual item, Search all modules with a keyword in their synopsis line, and go to the Module index, Topics and Keywords pages.
When :program:`pydoc` generates documentation, it uses the current environment
and path to locate modules. Thus, invoking :program:`pydoc spam`
documents precisely the version of the module you would get if you started the
Python interpreter and typed import spam.
Module docs for core modules are assumed to reside in
https://docs.python.org/X.Y/library/ where X and Y are the
major and minor version numbers of the Python interpreter. This can
be overridden by setting the :envvar:`PYTHONDOCS` environment variable
to a different URL or to a local directory containing the Library
Reference Manual pages.
.. versionchanged:: 3.2 Added the ``-b`` option.
.. versionchanged:: 3.3 The ``-g`` command line option was removed.
.. versionchanged:: 3.4 :mod:`pydoc` now uses :func:`inspect.signature` rather than :func:`inspect.getfullargspec` to extract signature information from callables.
.. versionchanged:: 3.7 Added the ``-n`` option.
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