Working with interfaces in separate files not working?

[nagreme]

I've implemented an interface in one file let's call it A.py:

from interface import Interface

class A(Interface):
  def method1(self):
    pass

And when I try to import and use it in another file, say B.py:

from interface import implements
import A

class B(implements(A)):
  def method1(self):
    print("foo")

b = B()
b.method1()

When I run B.py or whenever I try to import B I get this error:

Traceback (most recent call last):
  File "B.py", line 4, in <module>
    class B(implements(A)):
  File "/home/nagreme/.local/lib/python3.6/site-packages/interface/interface.py", line 490, in implements
    if not issubclass(I, Interface):
TypeError: issubclass() arg 1 must be a class

If I put the implementation of A in the same file it works but that isn't really convenient for bigger projects with several more complex implementing classes: is there any way to fix this or work around it?

[ssanderson]

@nagreme your import A line is giving you the module object defined by A.py, not the A interface defined within that module.

You want to change your second example to something like:

from interface import implements
from A import A

class B(implements(A)):
  def method1(self):
    print("foo")

b = B()
b.method1()

or, equivalently

from interface import implements
import A  # A is the A.py module

class B(implements(A.A)):  # A.A is the A class that's part of the module.
  def method1(self):
    print("foo")

b = B()
b.method1()

[nagreme]

Ah oops I just realized that! Thank you for your response, this is a great project!