# a.py
lazy import b

def something():
    b.hello()

something()

# b.py
lazy import a

def hello():
    print(a)

Python/gc.c:533: visit_decref: Assertion "!_PyObject_IsFreed(op)" failed
Enable tracemalloc to get the memory block allocation traceback

object address  : 0x7fcfb75797f0
object refcount : 2
object type     : 0x55a7d0ea0140
object type name: dict
object repr     : [1]    38419 segmentation fault (core dumped)  /home/peter/develop/cpython/python a.py

Traceback (most recent call last):
  File "/home/peter/develop/cpython/b.py", line 1, in <module>
    lazy import a
ImportError: deferred import of 'a' raised an exception during resolution

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/peter/develop/cpython/a.py", line 6, in <module>
    something()
    ~~~~~~~~~^^
  File "/home/peter/develop/cpython/a.py", line 4, in something
    b.hello()
    ~~~~~~~^^
  File "/home/peter/develop/cpython/b.py", line 4, in hello
    print(a)
          ^
  File "/home/peter/develop/cpython/a.py", line 6, in <module>
    something()
    ~~~~~~~~~^^
  File "/home/peter/develop/cpython/a.py", line 4, in something
    b.hello()
    ~~~~~~~^^
  File "/home/peter/develop/cpython/b.py", line 4, in hello
    print(a)
          ^
ImportCycleError: cannot import name 'a' (most likely due to a circular import)