CODEWITHSUNDEEP
python
Onza
Onza

Reputation: 1830

Python, split a module into several files

I have a module which can be described as python

class Symbol():
    def __init__(data):
        self.data = data
        pass
    def __add__(self,other):
        return Add(self,other)

class Integer(Symbol):
    pass

class Add(Symbol):
    def __init__(a,b):
        self.data = [a,b]

I want to split it into three files, which are symbol.py, integer.py and add.py; there are of course going to be a lot more details on those classes so having them in one files is ridiculous.

For some reason the imports never seem to work, while it's not even complaining of circular dependencies, can someone give me a little example?

Upvotes: 2

Views: 340

Answers (1)

Blckknght
Blckknght

Reputation: 104682

Your circular dependency situation isn't unsolvable, because Symbol doesn't depend on Add at definition time, only when the __add__ method is called. There are two good ways to resolve it.

The first is to not have the module Symbol is in import Add at top level, but only do that within the __add__ method itself. For instance, if your modules were named after the classes (only lowercase), you'd use this in symbol.py:

class Symbol():
    # ...

    def __add__(self,other):
        from add import Add
        return Add(self,other)

The other approach is to import Add globally into the symbol module, but do so after the definintion of the Symbol class. This way, when the add module imports symbol back, it will always be able to see the Symbol class's definition, even if the rest of the module is not finished loading.

class Symbol():
    # same as in your current code

from add import Add

If you go with this second approach and the Symbol class imports other stuff at the top of the file (where import statements normally are put), you might want to add a comment in that space about Add being imported later (and why).

Upvotes: 1

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