Question

I have a list that I’m attempting to remove duplicate items from. I’m using python 2.7.1 so I can simply use the set() function. However, this reorders my list. Which for my particular case is unacceptable.

Below is a function I wrote; which does this. However I’m wondering if there’s a better/faster way. Also any comments on it would be appreciated.

    def ordered_set(list_):

        newlist = []
        lastitem = None
        for item in list_:

            if item != lastitem:
                newlist.append(item)
                lastitem = item

        return newlist

The above function assumes that none of the items will be None, and that the items are in order (ie, [‘a’, ‘a’, ‘a’, ‘b’, ‘b’, ‘c’, ‘d’])

The above function returns [‘a’, ‘a’, ‘a’, ‘b’, ‘b’, ‘c’, ‘d’] as [‘a’, ‘b’, ‘c’, ‘d’].

Answer 1

Use an OrderedDict:

from collections import OrderedDict

l = ['a', 'a', 'a', 'b', 'b', 'c', 'd']
d = OrderedDict()

for x in l:
    d[x] = True

# prints a b c d
for x in d:
    print x,
print