best way to compare contents of 2 lists?

Esmail ebonak at hotmail.com
Fri Apr 24 03:51:42 CEST 2009


David Robinow wrote:
> On Thu, Apr 23, 2009 at 9:31 PM, Esmail <ebonak at hotmail.com> wrote:
>> What is the best way to compare the *contents* of two different
>> lists regardless of their respective order? The lists will have
>> the same number of items, and be of the same type.
>>
>> E.g. a trivial example (my lists will be larger),
>>
>> a=[1, 2, 3]
>>
>> b=[2, 3, 1]
>>
>> should yield true if a==b
>>
>> I suppose I could sort them and then compare them. I.e.,
>>
>> sorted(a)==sorted(b)
>>
>>
>> I am wondering if there is a more efficient/preferred way to do so.
>>
>> Thanks,
>> Esmail
>>
>> --
>> http://mail.python.org/mailman/listinfo/python-list
>>
> 
> set(a) == set(b)    # test if a and b have the same elements
> 
> # check that each list has the same number of each element
> # i.e.    [1,2,1,2] == [1,1,2,2], but [1,2,2,2] != [1,1,1,2]
> for elem in set(a):
>   a.count(elem) == b.count(elem)

Ah .. this part would take care of different number of duplicates
in the lists. Cool.

thanks,
Esmail

> --
> http://mail.python.org/mailman/listinfo/python-list
> 




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