Source code: Lib/pydoc.py
The 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 __doc__ attribute) of the object,
and recursively of its documentable members. If there is no docstring,
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 inspect.getcomments()).
The built-in function help() invokes the online help system in the
interactive interpreter, which uses 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 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 sys module, in a
style similar to the manual pages shown by the Unix man command. The
argument to 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 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, 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, pydoc attempts to paginate the
output for easier reading. If the PAGER environment variable is set,
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 man command. The synopsis line of a
module is the first line of its documentation string.
You can also use pydoc to start an HTTP server on the local machine
that will serve documentation to visiting Web browsers. 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.
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 pydoc generates documentation, it uses the current environment
and path to locate modules. Thus, invoking 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 PYTHONDOCS environment variable
to a different URL or to a local directory containing the Library
Reference Manual pages.
Changed in version 3.2: Added the -b option.
Changed in version 3.3: The -g command line option was removed.
Changed in version 3.4: pydoc now uses inspect.signature() rather than
inspect.getfullargspec() to extract signature information from
callables.