Chris Rebert pyideas-QkDgq5C4a+JWk0Htik3J/w@public.gmane.org writes:
On Tue, Oct 18, 2011 at 7:14 PM, Nikolaus Rath Nikolaus@rath.org wrote:
Hello,
I often have code of the form:
def my_fun(): allocate_res1() try: # do stuff allocate_res2() try: # do stuff allocate_res3() try: # do stuff finally: cleanup_res3() finally: cleanup_res2() finally: cleanup_res1()
return
With increasing number of managed resources, the indentation becomes really annoying, there is lots of line noise, and I don't like the fact that the cleanup is so far away from the allocation.
Use the with statement and context managers. They were added for
this exact situation.
See http://www.python.org/dev/peps/pep-0343/
Resulting code will resemble:
def func(): with alloc() as res1, alloc() as res2, alloc() as res3:
# do stuff
I think they're not for exactly this situation for two reasons:
This requires the alloc() functions to be context managers. If they're not, then I need to code a wrapping context manager as well. It's probably possible to write a generic wrapper that works for any cleanup function, but the result is not going to look very nice.
If I don't want to allocate the resources all at the same time, the indentation mess is still the same:
def func(): with alloc() as res1:
# do stuff
with alloc() as res2:
# do stuff
with alloc() as res3:
# do stuff
Best,
-Nikolaus
-- »Time flies like an arrow, fruit flies like a Banana.«
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