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+--- Thread: what works with the with statement? (/thread-35957.html)
what works with the with statement? - Skaperen - Jan-02-2022
is there a list of everything that works with the with statement? or, alternatively, everything that does not work with the with statement? i could not find anything at all, one way or the other, regarding how a particular function behaved, so i had to set up a test script.
import os
with os.open('/dev/tty',os.O_WRONLY) as fd:
write(fd,b'foo\n')
write(fd,b'bar\n')i don't want to have to do this with everything i might use the with statement with.
RE: what works with the with statement? - BashBedlam - Jan-03-2022
(Jan-02-2022, 11:19 PM)Skaperen Wrote: is there a list of everything that works with the with statement? or, alternatively, everything that does not work with the with statement? i could not find anything at all, one way or the other, regarding how a particular function behaved, so i had to set up a test script.What you can search for is "Context Manager". I think that you'll get more information that way. I can't tell you what does or does not qualify as a context manager but if you want to have some fun fooling around with the idea, you can roll your own. Try this:
from time import time
class Timer : # This is your context manager :)
def __enter__ (self) :
self.start = time ()
return self
def __exit__ (self, *args) :
end = time ()
self.interval = end - self.start
with Timer () as tracker:
for count in range (99999) :
print ('Still working...')
print(f'The loop took {tracker.interval:.3f} seconds.')
RE: what works with the with statement? - Gribouillis - Jan-03-2022
If an object has an
__enter__() method and an __exit__() method, you can normally use it with the with statement.
RE: what works with the with statement? - DeaD_EyE - Jan-03-2022
First attempt to get filename where __enter__ occours:
grep -Rl __enter__ .pyenv/versions/3.11.0a3 | egrep ".py$" | xargs -n1 basename | egrep -v "^test|^_" | sort -uTo gather more information, you have to use some functions from inspect.
RE: what works with the with statement? - Gribouillis - Jan-03-2022
It is more difficult to track objects returned by functions from the contextlib module, such as functions decorated by the
contextmanager decorator. They are functions that return contexts.
RE: what works with the with statement? - Skaperen - Jan-05-2022
i made my zopen() class work with with statements (tested). but i was, at first, surprised that os.open() did not work with with. thinking about it, since it returns int, that makes sense.
RE: what works with the with statement? - Gribouillis - Jan-05-2022
You could wrap it in a context manager
import contextlib
import os
@contextlib.contextmanager
def osopen(*args, **kwargs):
fd = os.open(*args, **kwargs)
try:
yield fd
finally:
os.close(fd)
s = b'hello world'
with osopen('foo.txt', os.O_WRONLY|os.O_CREAT, 0o666) as fd:
while s:
n = os.write(fd, s)
s = s[n:]
RE: what works with the with statement? - Skaperen - Jan-06-2022
that justifies me digging into more documentation to learn what magic decorators really do.