Question

I am having trouble with this setup mainly because I am not sure what I actually want in order to solve this problem.

This is the setup

- main.py
- lib
  - __init__.py 
  - index.py
  - test.py

__init__.py has this code

import os
for module in os.listdir(os.path.dirname(__file__)+"/."):
    if module == '__init__.py' or module[-3:] != '.py':
        continue
    __import__(module[:-3], locals(), globals())
del module

main.py has this code as of now

from lib.index import *
print User.__dict__

index.py has this code

class User(object):
    def test(self):
        return "hi"
    pass

test.py has this code

class User(object):
    def tes2(self):
        return "hello"

When I execute main.py it successfully prints the method test from index.py but what I am trying to do is figure out a way where I can just create a file in the lib folder where that while has only one function in the format

class User(object):
    def newFunction(self):
       return abc

and this function should automatically be available for me in main.py

I am sure that this is not a hard thing to do but I honestly don’t know what I want (what to search for to solve this) which is preventing me from researching the solution.

Answer 1

You can use a metaclass to customize class creation and add functions defined elsewhere:

import types
import os
import os.path
import imp

class PluginMeta(type):
    def __new__(cls, name, bases, dct):
        modules = [imp.load_source(filename, os.path.join(dct['plugindir'], filename))
                    for filename in os.listdir(dct['plugindir']) if filename.endswith('.py')]
        for module in modules:
            for name in dir(module):
                function = getattr(module, name)
                if isinstance(function, types.FunctionType):
                    dct[function.__name__] = function
        return type.__new__(cls, name, bases, dct)


class User(metaclass=PluginMeta):
    plugindir = "path/to/the/plugindir"

    def foo(self):
        print "foo"

user = User()
print dir(user)

Then in the plugin files, just create functions not classes:

def newFunction(self, abc):
    self.abc = abc
    return self.abc

And the metaclass will find them, turn them into methods, and attach them to your class.