PythonAdvanced

Context Managers

Python context managers and the with statement: manage resources safely, build custom managers, and use contextlib decorators.

01With statement for files

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main.py

with open("data.txt", "w") as f:
    f.write("Python")

with open("data.txt") as f:
    print(f.read())

Output

Python

02Custom context manager

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main.py

class Timer:
    def __enter__(self):
        print("Start")
        return self
    def __exit__(self, *args):
        print("End")

with Timer():
    print("Working")

Output

Start
Working
End

03contextlib decorator

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main.py

from contextlib import contextmanager

@contextmanager
def tag(name):
    print("<" + name + ">")
    yield
    print("</" + name + ">")

with tag("div"):
    print("content")

Output

<div>
content
</div>