On Wednesday, September 7, 2016 at 8:25:42 PM UTC-4, p...@blacktoli.com wrote:
> Hello,
>
> any ideas why this does not work?
>
> >>> def add(key, num):
> ... a[key] += num
> ...
> >>> a={}
> >>> a["007-12"] = 22 if not a.has_key("007-12") else add("007-12",22)
> >>> a
> {'007-12': 22} # OK here, this is what I want
> >>> a["007-12"] = 22 if not a.has_key("007-12") else add("007-12",22)
> >>> a
> {'007-12': None} # why does this became None?
>
> Thanks
Your add() function returns None (because it has no return statements).
Your failing statement is assigning that None to a["007-12"].
There are a number of helpful structures in Python to do this work for
you. collections.Counter will probably be helpful:
>>> from collections import Counter
>>> a = Counter()
>>> a["007-12"] += 22
>>> a
Counter({'007-12': 22})
>>> a["007-12"] += 22
>>> a
Counter({'007-12': 44})
--Ned.
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