> Subject: Re: [Tutor] Appending an extra column in a data file
>
> On Wed, Apr 10, 2013 at 5:49 PM, Oscar Benjamin
> <oscar.j.benja...@gmail.com> wrote:
>>> fin = open('old.dat')
>>> fout = open('new.dat', 'w')
>>>
>>> with fin, fout:
>>> for line in fin:
>>
>> This has the same problems as contextlib.nested: An error raised while
>> opening 'new.dat' could prevent 'old.dat' from being closed
> properly.
>
> Thanks for pointing out the potential bug there. It's not a big
> problem in this case with the file open for reading. But, yeah, I'm
> hanging my head in shame here... ;)
Cool. This solves a problem it had with contextlib.nested some time ago.
(sorry for kinda hijacking this thread, but..)
Would it be safe (both __exit__ calls are guaranteed to be made) to use
code like this (if it worked, that is!)?
import sys
import contextlib
def someCloseFunc():
print "Yaaay properly closed!"
@contextlib.contextmanager
def funcOne(arg):
e = None
try:
yield arg
except:
e = sys.exc_info()[1]
print e
finally:
someCloseFunc()
if e:
yield e
yield None
funcTwo = funcOne
with contextlib.nested(funcOne("one-ish"), funcTwo("two-ish")) as (one, two):
print one, two
* traceback
one-ish two-ish
Yaaay properly closed!
generator didn't stop
Yaaay properly closed!
Traceback (most recent call last):
File "F:/mgr.py", line 23, in <module>
print one, two
File "C:\Program Files\Python27\lib\contextlib.py", line 24, in __exit__
self.gen.next()
File "C:\Program Files\Python27\lib\contextlib.py", line 121, in nested
if exit(*exc):
File "C:\Program Files\Python27\lib\contextlib.py", line 36, in __exit__
raise RuntimeError("generator didn't stop after throw()")
RuntimeError: generator didn't stop after throw()
>>>
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