Nick Coghlan ncoghlan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org writes:
On Wed, Oct 19, 2011 at 1:14 PM, Chris Rebert pyideas-QkDgq5C4a+JWk0Htik3J/w@public.gmane.org wrote:
On Tue, Oct 18, 2011 at 7:14 PM, Nikolaus Rath Nikolaus-BTH8mxji4b0@public.gmane.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
Or, to more closely mirror the original example:
# Define these wherever the current resources are defined
@contextlib.contextmanager
def cm1():
res1 = allocate_res1()
try:
yield res1
finally:
cleanup_res1()
@contextlib.contextmanager
def cm2():
res2 = allocate_res2()
try:
yield res2
finally:
cleanup_res2()
@contextlib.contextmanager
def cm3():
res3 = allocate_res3()
try:
yield res2
finally:
cleanup_res3()
def func():
with cm1() as res1:
# do stuff
with cm2() as res2:
# do stuff
with cm3() as res3:
# do stuff
Indeed, that works. But I do you really consider this code nicer than the original one? I think a simple line count answers the question :-).
Best,
-Nikolaus
-- »Time flies like an arrow, fruit flies like a Banana.«
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