iritkatriel@Irits-MBP cpython % cat exc.py class A: class B: class E(Exception): pass raise A.B.E() iritkatriel@Irits-MBP cpython % cat test.py import exc iritkatriel@Irits-MBP cpython % ./python.exe test.py Traceback (most recent call last): File "/Users/iritkatriel/src/cpython/test.py", line 2, in <module> import exc ^^^^^^^^^^ File "/Users/iritkatriel/src/cpython/exc.py", line 7, in <module> raise A.B.E() ^^^^^^^^^^^^^ exc.E ============== See the last line of the output: there is no such thing as exc.E. There is exc.A.B.E. The traceback module doesn't have this issue: iritkatriel@Irits-MBP cpython % cat test.py import traceback try: import exc except Exception as e: traceback.print_exception(e) iritkatriel@Irits-MBP cpython % ./python.exe test.py Traceback (most recent call last): File "/Users/iritkatriel/src/cpython/test.py", line 5, in <module> import exc ^^^^^^^^^^ File "/Users/iritkatriel/src/cpython/exc.py", line 7, in <module> raise A.B.E() ^^^^^^^^^^^^^ exc.A.B.E