"pydoc" --- 文件產生器與線上幫助系統
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**原始碼：**Lib/pydoc.py

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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

   python -m 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.

備註:

  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.
**python -m 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.

**python -m 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.

**python -m 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.

在 3.2 版的變更: 新增 "-b" 選項。

在 3.3 版的變更: The "-g" command line option was removed.

在 3.4 版的變更: "pydoc" now uses "inspect.signature()" rather than
"inspect.getfullargspec()" to extract signature information from
callables.

在 3.7 版的變更: 新增 "-n" 選項。
