list to dict

[Josef Dalcolmo]

on Wed, 16 Jun 2004 09:29:23 -0400
Bart Nessux <bart_nessux at hotmail.com> wrote:

> What is the easiest/fastest way to build a dictionary from a list? The 
> list contains 100,000 entries.

The first question would be, what should the keys be? If the list consists of unique, unmutable items, then you might use the items themselves as key and write:

mydict = dict(zip(mylist, mylist))

obtaining a dictionary with all the keys and values identical (therefore somewhat of a waste, but occasionally useful). Note: if your original list did not contain unique values, you end up with a set.

If you want to remember the original order of the list, then write

mydict = dict(zip(mylist, xrange(len(mylist))))


If you don't care about the key (that would be strange) then you can write:

mydict = dict(zip(xrange(len(mylist)), mylist))

Instead of len(mylist) you can also write 1000000 or any other number larger than your list.
 

- Josef