Resetting Globals With Importing

Question

I have this code (Reset.py) that works how I want it to unless I import it.

class Res(object):
    defaults={}
    class NoKey: pass
    def __init__(self):
        for key, values in defaults.items():
            globals()[key]=values
    def add_defaults(key, values):
        Res.defaults[key]=value
    def remove_defaults(key=NoKey, remove_all=False):
        if remove_all:
            Res.defaults={}
        else:
            del Res.defaults[key]

Without importing:

>>> a=54
>>> Res.add_default('a', 3)
>>> Res()
<__main__.Res object at 0x>
>>> a
3
>>> #great! :D

With importing:

>>> a=54
>>> Res.add_default('a', 3)
>>> Res()
<Reset.Res object at 0x>
>>> a
54

This must mean when it is imported it changes the globals() under Reset and not __main__. How can I fix this?

[Edited defaults to Res.defaults under remove_defaults (defaults was not a global variable).]

Answer 1

You don't fix this: it isn't broken. Mutating globals, especially implicitly mutating globals within another module's namespace, is a very bad idea that leads to confusing, unmaintainable, untestable code.

Your design seems really confusing. Res doens't really seem to be a class. Most of it's methods aren't methods at all (they aren't mutating some state stored in self); the only one that is defined like a method is your __init__, which won't work (defaults shouldn't be defined from the snippet given; the class namespace only looks up there during the original definition of the class. Do you have another thing, a global named defaults?) If you are trying to use Res to group related stuff, don't use a class for that; that's what modules are for in Python.

Perhaps you should post a question describing the problem you are solving. I suspect this code indicates a very suboptimal design.