On 2010-03-04 15:19 PM, Mike Kent wrote:
On Mar 3, 12:00 pm, Robert Kern<robert.k...@gmail.com> wrote:
On 2010-03-03 09:39 AM, Mike Kent wrote:
What's the compelling use case for this vs. a simple try/finally?
original_dir = os.getcwd()
try:
os.chdir(somewhere)
# Do other stuff
finally:
os.chdir(original_dir)
# Do other cleanup
A custom-written context manager looks nicer and can be more readable.
from contextlib import contextmanager
import os
@contextmanager
def pushd(path):
original_dir = os.getcwd()
os.chdir(path)
try:
yield
finally:
os.chdir(original_dir)
with pushd(somewhere):
...
Robert, I like the way you think. That's a perfect name for that
context manager! However, you can clear one thing up for me... isn't
the inner try/finally superfluous? My understanding was that there
was an implicit try/finally already done which will insure that
everything after the yield statement was always executed.
No, the try: finally: is not implicit. See the source for
contextlib.GeneratorContextManager. When __exit__() gets an exception from the
with: block, it will push it into the generator using its .throw() method. This
raises the exception inside the generator at the yield statement.
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
--
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