Source: 📖 Effective Python order 66

Using contextmanager to use custom functions in with statements

Any time that repeated use of try/finally clauses is needed, consider using the contextmanager decorator from the contextlib module. This decorator allows you to specify the setup behaviour that will be executed when the with statement is declared (the try block) and the tear-down behaviour that will be executed when the with block ends.

import os
from contextlib import contextmanager

def change_directory(destination):
	try:
		original_dir = os.getcwd()
		os.chdir(destination)
		yield
	finally:
		os.chdir(original_dir)

with change_directory('my_dir_1'):
	# do some stuff

The above function can now be used to jump in and out of different directories without needing to remember to change back to the original directory. Not only is this cleaner to read, but it is also safer as it ensures that resources are properly managed and nothing is left open after it is no longer needed for processing within the code, as it will automatically be closed by the finally block at the time that the with block ends.

See also:

• Generator expressions explained