Avoiding circular (cyclic) imports in Python?

Question

One way is to use import x, without using "from" keyword. So then you refer to things with their namespace everywhere.

Is there any other way? like doing something like in C++ ifnotdef __b__ def __b__ type of thing?

Answer 1

Merge any pair of modules that depend on each other into a single module. Then introduce extra modules to get the old names back.

E.g.,

# a.py
from b import B

class A: whatever

# b.py
from a import A

class B: whatever

becomes

# common.py
class A: whatever
class B: whatever

# a.py
from common import A

# b.py
from common import B

Answer 2

Circular imports are a "code smell," and often (but not always) indicate that some refactoring would be appropriate. E.g., if A.x uses B.y and B.y uses A.z, then you might consider moving A.z into its own module.

If you do think you need circular imports, then I'd generally recommend importing the module and referring to objects with fully qualified names (i.e, import A and use A.x rather than from A import x).