Getting a list of all modules

Robert Kern robert.kern at
Wed Jul 30 12:35:41 CEST 2014

On 2014-07-30 09:46, Peter Otten wrote:
> Steven D'Aprano wrote:
>> I'm looking for a programmatic way to get a list of all Python modules
>> and packages. Not just those already imported, but all those which
>> *could* be imported.
>> I have a quick-and-dirty function which half does the job:
>> def get_modules():
>>      extensions = ('.py', '.pyc', '.pyo', '.so', '.dll')
>>      matches = set()
>>      for location in sys.path:
>>          if location == '': location = '.'
>>          if os.path.isdir(location):
>>              for name in os.listdir(location):
>>                  base, ext = os.path.splitext(name)
>>                  if ext in extensions:
>>                      matches.add(base)
>>      return sorted(matches)
>> but I know it's wrong (it doesn't handle packages correctly, or zip
>> files, doesn't follow .pth files, has a very naive understanding of cross-
>> platform issues, fails to include built-in modules that don't live in the
>> file system, and probably more).
>> Is this problem already solved? Can anyone make any suggestions?
> $ python3 -m pydoc -b
> shows a page with modules that I think is more complete than what you have.
> A quick glance at the implementation suggests that the hard work is done by
> pkgutil.iter_modules()

There are two niggles to this answer: it omits builtin modules, but those are 
easily discovered through sys.builtin_module_names. It can also include spurious 
script .py files that cannot be imported because their names are not Python 
identifiers: e.g. Those are easy to filter out, fortunately.

Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco

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