What do you mean by "command"? Python does not have commands as such.
If you mean the Python keywords, then you can find that out from the keywords module:
If you mean the builtin functions then you can find them at http://www.python.org/doc/2.3.3/lib/built-in-funcs.html.
>>> import keyword
['and', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'exec', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'not', 'or', 'pass', 'print', 'raise', 'return', 'try', 'while', 'yield']
If you mean all the libraries as well, then RTFM at http://www.python.org/doc/2.3.3/lib/lib.html.
If you want include all the third-party libraries and extensions, then you are out of luck, since I doubt a complete list exists in one place. Even if it did it would be out of date almost immediately, since new stuff is being written all the time.
Dave - The Developers' Coach