Error Handling Internals — Series 2

Preview — 3 of 10 questions

What is the output of the following code?

javascript

class AlwaysTrue:
    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, tb):
        print("exit called, exc_type =", exc_type)
        return True

with AlwaysTrue():
    print("no exception here")

print("after block")

Ano exception here, exit called, exc_type = None, then the block re-executes indefinitely, since __exit__ returned True.

Bexit called, exc_type = None, no exception here, after block

Cno exception here, after block — __exit__ is only called when an exception actually occurs.

Dno exception here, exit called, exc_type = None, after block

What is the output of the following code?

javascript

import sys

original_hook = sys.excepthook

def custom_hook(exc_type, exc_value, tb):
    print(f"custom handler: {exc_type.__name__}: {exc_value}")

sys.excepthook = custom_hook
print(sys.excepthook is custom_hook)

sys.excepthook = original_hook
print(sys.excepthook is original_hook)

ATrue, True

BFalse, True — sys.excepthook cannot be reassigned to an arbitrary function; only specific pre-registered callables are accepted.

CTypeError: excepthook is read-only

DTrue, False — restoring sys.excepthook to its original value afterward silently fails.

What is the output of the following code?

javascript

from contextlib import ExitStack

def setup():
    stack = ExitStack()
    stack.callback(lambda: print("cleanup A"))
    stack.callback(lambda: print("cleanup B"))
    return stack.pop_all()

transferred = setup()
print("using resources")
transferred.close()

Acleanup A, cleanup B, using resources — pop_all() immediately triggers all registered cleanups before returning.

Busing resources, cleanup B, cleanup A

Cusing resources only — pop_all() silently discards every registered callback instead of transferring them.

Dusing resources, cleanup A, cleanup B

Answer all 10 questions (7 more), see explanations for every answer, and track your score.