ModulesAsPlugins

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Here’s how to find all the modules in some directory, and import them.

Finding Modules in a Directory

Is there a better way than just listing the contents of the directory, and taking those tiles that end with “.pyc” or “.py”..?

But perhaps there isn’t.

   1 import os
   2 
   3 def find_modules(path="."):
   4     """Return names of modules in a directory.
   5 
   6     Returns module names in a list. Filenames that end in ".py" or
   7     ".pyc" are considered to be modules. The extension is not included
   8     in the returned list.
   9     """
  10     modules = set()
  11     for filename in os.listdir(path):
  12         module = None
  13         if filename.endswith(".py"):
  14             module = filename[:-3]
  15         elif filename.endswith(".pyc"):
  16             module = filename[:-4]
  17         if module is not None:
  18             s.add(module)
  19     return list(modules)

Importing the Modules

How do you import a module, once you have it’s name?

With the ImpModule! It dynamically loads named modules.

   1 import imp
   2 
   3 def load_module(name, path=["."]):
   4     """Return a named module found in a given path."""
   5     (file, pathname, description) = imp.find_module(name, path)
   6     return imp.load_module(name, file, pathname, description)
   7 
   8 modules = [load_module(name) for name in find_modules()]

Finding the Things Inside a Module

Once you have your module, you can look inside it, with .__dict__.

   1 module.__dict__

Finding Functions Within a Module

We just look for dictionary values that are of type types.FunctionType.

   1 def functions_in_module(module)
   2     functions = []
   3     for obj in module.__dict__.values():
   4         if isinstance(obj, types.FunctionType):
   5             functions.append(obj)
   6     return functions

See Also

The DocXmlRpcServer page includes code demonstrating the use of these techniques.

Discussion

I got this error when executing find_modules() in a package directory. That is the directory contained an  __init.py__ file:

  File "C:\Python254\lib\site-packages\joedorocak\find_modules.py", line 27, in find_modules
    s.add(module)
NameError: global name 's' is not defined

It looks to me like s needs to be initialized (some place near “modules = set()”). I’m not sure what the protocol is here, so I’m just going to leave this comment in the discussion.

Here’s what seems to work for me. I got rid of ‘s’ altogether.

def find_modules(path="."):
    """Return names of modules in a directory.

    Returns module names in a list. Filenames that end in ".py" or
    ".pyc" are considered to be modules. The extension is not included
    in the returned list.
    """
    modules = set()
    for filename in os.listdir(path):
        module = None
        if filename.endswith(".py"):
            module = filename[:-3]
        elif filename.endswith(".pyc"):
            module = filename[:-4]
        if module is not None:
            modules.add(module)
    return list(modules)

All the best,

JoeDorocak