Python · Theory

Context Manager in Python

Theory

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Context Manager in Python

A context manager sets up and cleans up automatically. with expression as var: guarantees cleanup on the way out — even if an error fires. Files: with open(path) as f:. You can write your own with __enter__ / __exit__ or contextlib. Mental model: acquire, use, release. with is safer than open + close that you might forget.

Why with beats manual close() — an exception in the middle still closes the file. That sentence is the viva.

Context Manager in Python — output — Hi. with guarantees close — same idea as with open("a.txt").

Exam tip

Why with is safer than manual close().

Example

# Context manager
from contextlib import closing
from io import StringIO
with closing(StringIO("Hi")) as f:
    print(f.read())

Context Manager in Python — output: Hi. with guarantees close — same idea as with open("a.txt").

Short notes

Defwith = setup + cleanup.
RuleFile example first.
Remember__enter__ / __exit__.

Python · Theory

Context Manager in Python

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Theory

73/268

Context Manager in Python

Why with beats manual close() — an exception in the middle still closes the file. That sentence is the viva.

Context Manager in Python — output — Hi. with guarantees close — same idea as with open("a.txt").

Exam tip

Why with is safer than manual close().

Example

# Context manager
from contextlib import closing
from io import StringIO
with closing(StringIO("Hi")) as f:
    print(f.read())

Context Manager in Python — output: Hi. with guarantees close — same idea as with open("a.txt").

Short notes

Defwith = setup + cleanup.
RuleFile example first.
Remember__enter__ / __exit__.

Context Manager in Python

Example

Short notes

Questions

Context Manager in Python

Example

Short notes

Questions