Importing modules inside python class

I’m currently writing a class that needs os, stat and some others.

What’s the best way to import these modules in my class?

I’m thinking about when others will use it, I want the ‘dependency’ modules to be already imported when the class is instantiated.

Now I’m importing them in my methods, but maybe there’s a better solution.

Answer

If your module will always import another module, always put it at the top as PEP 8 and the other answers indicate. Also, as @delnan mentions in a comment, sys, os, etc. are being used anyway, so it doesn’t hurt to import them globally.

However, there is nothing wrong with conditional imports, if you really only need a module under certain runtime conditions.

If you only want to import them if the class is defined, like if the class is in an conditional block or another class or method, you can do something like this:

condition = True

if condition:
    class C(object):
        os = __import__('os')
        def __init__(self):
            print self.os.listdir

    C.os
    c = C()

If you only want it to be imported if the class is instantiated, do it in __new__ or __init__.