splitting one dictionary into two

[Raymond Hettinger]

[jsaul][color=blue]
> I have to split a dict into two dicts. Depending on their values,
> the items shall remain in the original dict or be moved to another
> one and at the same time be removed from the original dict.
>
> OK, this is how I do it right now:
>
> dict1 = { "a":1, "b":3, "c":5, "d":4, "e":2 }
> dict2 = {}
> klist = []
>
> for key in dict1:
> if dict1[key] > 3: # some criterion
> dict2[key] = dict1[key]
> klist.append(ke y)
>
> for key in klist:
> del dict1[key]
>
> print dict1
> print dict2
>
> That means that I store the keys of the items to be removed from
> the original dict in a list (klist) and subsequently remove the
> items using these keys.
>
> Is there an "even more pythonic" way?[/color]

Your way seems clean enough to me.

One other approach is to use items() so you can modify dict1 as you go:

for key, value in dict1.items():
if value > 3:
dict2[key] = value
del dict1[key]



Raymond Hettinger

[wes weston]

Re: splitting one dictionary into two

Raymond Hettinger wrote:[color=blue]
> [jsaul]
>[color=green]
>>I have to split a dict into two dicts. Depending on their values,
>>the items shall remain in the original dict or be moved to another
>>one and at the same time be removed from the original dict.
>>
>>OK, this is how I do it right now:
>>
>> dict1 = { "a":1, "b":3, "c":5, "d":4, "e":2 }
>> dict2 = {}
>> klist = []
>>
>> for key in dict1:
>> if dict1[key] > 3: # some criterion
>> dict2[key] = dict1[key]
>> klist.append(ke y)
>>
>> for key in klist:
>> del dict1[key]
>>
>> print dict1
>> print dict2
>>
>>That means that I store the keys of the items to be removed from
>>the original dict in a list (klist) and subsequently remove the
>>items using these keys.
>>
>>Is there an "even more pythonic" way?[/color]
>
>
> Your way seems clean enough to me.
>
> One other approach is to use items() so you can modify dict1 as you go:
>
> for key, value in dict1.items():
> if value > 3:
> dict2[key] = value
> del dict1[key]
>
>
>
> Raymond Hettinger[/color]

Raymond,
I had the same approach seen above before the
originator added the fact that the starting
dictionaries would typically be "huge". Robert
Brewer timed this method as 5 times slower than
his method which showed me that my obsession with
simplicity needs to be looked at.
wes