CONTEXT MANAGERS In Python Are GENIUS!

What are context managers in Python? How can they give us more flexibility in our code? Let's find out together in this lesson!

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[sdmagic]

Really useful stuff. Thank you! I immediately implemented it in my database class.

[ntlake]

You can also use the @contextmanager decorator:

from contextlib import contextmanager

class File:
def __init__(self, path: str, mode: str):
self.path = path
self.mode = mode
self.is_open = True
def do_something(self):
if self.is_open:
print(f"Hi! This is a file. Its path is '{self.path}' and its mode is '{self.mode}'")
return
raise ValueError("this file is closed")
def close(self):
self.is_open = False

@contextmanager
def open_file(path: str, mode: str = "r"):
file = File(path, mode)
yield file
file.close()

with open_file(r"myfile.txt") as f:
f.do_something()

[enesguler]

I think it is a perfect feature. It may be useful for opening a video in OpenCV. Because I generally forget to close the video stream.

[daviddanielng]

Thanks, i have been thinking about writing my own context manager, but don't have the time to check the docs.

Thanks.

[wiseskeshom]

Thank you so much for this informative stuff.

[grzegorzryznar]

In a most cases it is easier to achieve with contextmanager decorator from contextlib:

@contextmanager
def open(name: str):
print(f'opening file: {name!r}')
yield 'return value'
print(f('closing file: {name!r}') # exit block

[rantalbott]

What gets called if you just fall out of the with block without an exception? Is there a "__else__" to make it consistent with loops? 😆

[teksimian]

python programmer can't find curly brackets 😂

[ConstantlyDamaged]

Any chance of an extra one on this showing operation of "async with"?

[RedShipsofSpainAgain]

2:04 how did you get that entire line of text to appear automatically? "def __exit__(self, exc_type, exc_val, exc_tb):"
Is it possible to do this in VS Code?

[wellygeek]

How do you implement __ENTER__ and __EXIT__ at the method level not class level?

[tamirshalev]

Thanks for the explanation! However, 'open' is a function rather than a class, so how does that work actually behins the scenes?

[dcknature]

Thank you so much for explaining context managers in Python 👍!
likes = 63 😉😉