Context Managers

3 tasks. Write the code, press Check, and the page runs it against a real Python interpreter.

Back to the context managers chapter

Exercise 1

Write a context manager class that prints start and end around the block.

Python

# define Section

with Section("build"):
    print("working")

class Section:
    def __init__(self, name):
        self.name = name

    def __enter__(self):
        print("start", self.name)
        return self

    def __exit__(self, exc_type, exc, tb):
        print("end", self.name)
        return False

with Section("build"):
    print("working")

Exercise 2

Write the same thing as a generator with @contextmanager.

Python

from contextlib import contextmanager

# define section

with section("build"):
    print("working")

from contextlib import contextmanager

@contextmanager
def section(name):
    print("start", name)
    try:
        yield
    finally:
        print("end", name)

with section("build"):
    print("working")

Exercise 3

Delete a file that may not exist, ignoring only that one error.

Python

import os
# remove never-existed.txt, then print done

import os
from contextlib import suppress

with suppress(FileNotFoundError):
    os.remove("never-existed.txt")

print("done")