Python: circular imports needed for type checking
- by phild
First of all: I do know that there are already many questions and answers to the topic of the circular imports.
The answer is more or less: "Design your Module/Class structure properly and you will not need circular imports". That is true. I tried very hard to make a proper design for my current project, I in my opinion I was successful with this.
But my specific problem is the following: I need a type check in a module that is already imported by the module containing the class to check against. But this throws an import error.
Like so:
foo.py:
from bar import Bar
class Foo(object):
def __init__(self):
self.__bar = Bar(self)
bar.py:
from foo import Foo
class Bar(object):
def __init__(self, arg_instance_of_foo):
if not isinstance(arg_instance_of_foo, Foo):
raise TypeError()
Solution 1: If I modified it to check the type by a string comparison, it will work. But I dont really like this solution (string comparsion is rather expensive for a simple type check, and could get a problem when it comes to refactoring).
bar_modified.py:
from foo import Foo
class Bar(object):
def __init__(self, arg_instance_of_foo):
if not arg_instance_of_foo.__class__.__name__ == "Foo":
raise TypeError()
Solution 2: I could also pack the two classes into one module. But my project has lots of different classes like the "Bar" example, and I want to seperate them into different module files.
After my own 2 solutions are no option for me: Has anyone a nicer solution for this problem?
