@contextmanager

Learn decorator-based context managers with @contextmanager.

@contextmanager

The @contextmanager decorator turns a function into a context manager. No need to write a class; a single yield separates opening and closing:

from contextlib import contextmanager

@contextmanager
def blok():
    print("başla")
    yield
    print("bitir")

with blok():
    print("içeride")

Code before yield acts as __enter__, code after as __exit__. This is shorter than writing a class.

The contextlib module is in the standard library.

yield and sending a value

yield can also return a value. This value is captured with as:

@contextmanager
def kaynak():
    print("aç")
    yield "veri"
    print("kapat")

with kaynık() as r:
    print(r)  # veri

Here yield "veri" is bound to r via as r. The value yielded is used inside the with block.

This corresponds to the return value of __enter__ in the class-based approach.

Exercise Write a block with @contextmanager

Write from contextlib import contextmanager. Define def blok(): with @contextmanager. In the body write print("başla"), yield, print("bitir"). Then inside with blok(): write print("içeride").

Show example solution

from contextlib import contextmanager

@contextmanager
def blok():
    print("başla")
    yield
    print("bitir")

with blok():
    print("içeride")

Test yourself

Match @contextmanager

@contextmanager

Decorator
yield

Split point
before yield

__enter__
after yield

__exit__
What does yield do in @contextmanager?
- Separates opening and closing
- Stops the block
- Raises an error
- Deletes a variable
Show answer

Separates opening and closing — Code before yield is opening, after is closing.

Complete the yield keyword

@contextmanager
def blok():
    print("başla")
    ____
    print("bitir")

Show answer

@contextmanager
def blok():
    print("başla")
    yield
    print("bitir")

Next lesson: Catching exceptions

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