A performance issue when using default value
wuwei23 at gmail.com
Mon Feb 1 06:20:53 CET 2010
alex23 <wuwe... at gmail.com> wrote:
> keakon <kea... at gmail.com> wrote:
> > def h2(x=):
> > y = x
> > y.append(1)
> > return y + 
> Are you aware that 'y = x' _doesn't_ make a copy of , that it
> actually points to the same list as x?
Sorry, I meant to suggest trying the following instead:
if x is None: x = 
return x + 
It's a common idiom to use None as a sentinel for this situation, esp.
where you _don't_ want a default mutable object to be reused.
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