dictionary total sum

[Joaquin Alzola]

On Wednesday, September 7, 2016 at 8:25:42 PM UTC-4, p... at 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})

Hi Ned

Also:
>>> a={}
>>> a["007-12"]=22
>>> a
{'007-12': 22}
>>> a["007-12"]+=22
>>> a
{'007-12': 44}
>>>

Will this fit his request?
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