Why are such imports not allowed?

Question

FILE: b.py

class B:
    def __init__(self):
        print "B"

import a

a = A()

FILE: a.py

class A(B):             ###=> B  is not  defined
    def __init__(self):
        print "A"

When I try to execute b.py, he said that B is not defined. I do not understand the "import"?

Thank you very much if you can point out the problem.

Answer 1

The next work on your code will be:

==== FILE: b.py ====

class B:
    def __init__(self):
        print "B"

import a

if __name__ == "__main__":
    a = a.A()

==== FILE: a.py ====
import b

class A(b.B):             ###=> B  is not  defined
    def __init__(self):
        print "A"

Please note the differences:

• Files (modules) are namespaces, if you import "a", you refer to its class A as "aA".

• You need to import b into a.py if you want to use it.

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Answer 2

python A . C PHP, .

B , A, . B c.py "from c import B".