Question

here’s 2 py file

aa.py

import bb
b = 3
bb.foo()

bb.py

import aa
def foo():
    print(aa.b)

when run from aa.py,this error came out

Traceback (most recent call last):
  File "D:\pyproj\Mytest\src\aa.py", line 7, in <module>
    import bb
  File "D:\pyproj\Mytest\src\bb.py", line 6, in <module>
    import aa
  File "D:\pyproj\Mytest\src\aa.py", line 9, in <module>
    bb.foo()
AttributeError: 'module' object has no attribute 'foo'

Another episode

just i want to solve the problem but i noticed something interesting or wired

i modified the test

aa.py

print('before import bb in aa.py')
import bb
print('after import bb in aa.py')
bb.foo()
print('end of all')

bb.py

def foo():
    print('before import aa in bb.foo()')
    import aa
    print('after import aa in bb.foo()')

start from aa.py

before import bb in aa.py
after import bb in aa.py
before import aa in bb.foo()
before import bb in aa.py
after import bb in aa.py
before import aa in bb.foo()
after import aa in bb.foo()
end of all
after import aa in bb.foo()
end of all

can anyone explain this?

Answer 1

The problem is a circular dependency: aa imports bb, which imports aa. Then aa calls bb.foo(), but this function has not yet been completely defined in bb, since the import of aa is not completed.

It is better to avoid such complex dependencies. What you can do is pass aa.b as an argument to bb.foo():

aa.py

import bb
b = 3
bb.foo(b)

bb.py

def foo(b):
    print(b)