python：class 名称未定义

Question

I am getting the error "name is not defined " when instantiating a class object in another file. what is causing this and how do I fix it? I know there are other posts with the same questions, but the fixes for those didn't work for me.

in classFile.py

class P:
    def __init__(self):
        pass
class C(P):
    def __init__(self):
        pass
if __name__ == "__main__":
    c1 = C() #no error

in main.py

import classFile
if __name__ == "__main__":
    foo = C() #errors

gives the error "C isn't defined".

when I instantiate foo as below, I get the error I get the error "classFile 'shelf' has no attribute 'C'

foo = classFile.C()

Answer 1

You need to explicitly mention you are using a class from classFile :

foo = classFile.C()

Alternatively, you could replace your import with:

from classFile import C

and keep your current usage.