ExitStack & Exception Groups

Preview — 3 of 10 questions

What is the output of the following code?

javascript

from contextlib import ExitStack

class Resource:
    def __init__(self, name):
        self.name = name
    def __enter__(self):
        print(f"open {self.name}")
        return self
    def __exit__(self, *args):
        print(f"close {self.name}")

names = ["a", "b", "c"]
with ExitStack() as stack:
    resources = [stack.enter_context(Resource(n)) for n in names]
    print("using all")

ATypeError: ExitStack() takes no arguments

Bopen a, open b, open c, using all, close c, close b, close a

Copen a, open b, open c, using all, close a, close b, close c

Dopen a, close a, open b, close b, open c, close c, using all

What is the output of the following code?

javascript

try:
    raise ExceptionGroup("multiple failures", [ValueError("bad value"), TypeError("bad type")])
except* ValueError as eg:
    print(f"caught ValueError group: {eg.exceptions}")
except* TypeError as eg:
    print(f"caught TypeError group: {eg.exceptions}")

AOnly the first matching except* clause runs, exactly like a regular except, catching everything.

BNeither except* clause runs; the ExceptionGroup propagates uncaught.

Ccaught ValueError group: (ValueError('bad value'),) then caught TypeError group: (TypeError('bad type'),)

DTypeError: except* cannot be used with ExceptionGroup

What is the output of the following code?

javascript

class Faulty:
    def __enter__(self):
        print("entering")
        raise RuntimeError("setup failed")

    def __exit__(self, *args):
        print("exiting")
        return False

try:
    with Faulty():
        print("using")
except RuntimeError as e:
    print(f"caught: {e}")

Aentering, using, exiting, caught: setup failed

Bentering, exiting, caught: setup failed — "using" is never printed.

CTypeError: __enter__() cannot raise exceptions

Dentering then caught: setup failed — "exiting" and "using" are never printed.

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