efficient list merging

François Pinard pinard at iro.umontreal.ca
Wed Sep 4 02:48:35 CEST 2002

[Christophe Delord]

>> I am not sure about the relative speed of everything, but I would be
>> tempted to try:
>>    dict(zip(list1 + list2, [None] * (len(list1) + len(list2)))).keys()
> This may be written using list comprehension:
>>>> dict([(k,1) for k in list1+list2]).keys()

The `for' loop, even within a list comprehension, will be compiled into an
explicit loop, likely to be slower than the implicit loops within `zip'.
Taking advantage of other clever suggestions, I would guess that:

    both = list1 + list2
    result = dict(zip(both, both)).keys()

would not be so bad, speed-wise.

François Pinard   http://www.iro.umontreal.ca/~pinard

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