Check for dict key existence, and modify it in one step.

Im using this construct a lot:

if dict.has_key(whatever):
dict[whatever] += delta
else:
dict[whatever] = 1

sometimes even nested:

if dict.has_key(whatever):
if dict[whatever].has_key(someother):
dict[whatever][someother] += delta
else:
dict[whatever][someother] = 1
else:
dict[whatever]={}
dict[whatever][someother] = 1

there must be a more compact, readable and less redundant way to do
this, no?

Thanks,

Rodrigo

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