How to delete duplicate values in a list?

Question

Possible Duplicate:
How do you remove duplicates from a list in Python whilst preserving order?

Let us consider the list:

x = ['a', 'b', 'c', 'c', 'a', 'd', 'z', 'z']

I want to delete these duplicate values list-x and want the result as:

y = ['a', 'b', 'c', 'd', 'z']

Answer 1

If ordering doesn't matter, use a set:

>>> list(set(['a', 'b', 'c', 'c', 'a', 'd', 'p', 'p']))
['a', 'p', 'c', 'b', 'd']

If ordering does matter, use an OrderedDict:

>>> from collections import OrderedDict 
>>> OrderedDict.fromkeys(['a', 'b', 'c', 'c', 'a', 'd', 'p', 'p']).keys()
['a', 'b', 'c', 'd', 'p']

Answer 2

Since nothing was stated about preserving order, this approach will work:

x = ['a', 'b', 'c', 'c', 'a', 'd', 'z', 'z']

list(set(x))

will give you

['a', 'c', 'b', 'd', 'z']

By changing your list to a set you eliminate all duplicates. You apply list() to change your non-duplicate data back to a list.

Answer 3

You could also use

y=[ x[i] for i in range(len(x)) if not x[i] in x[:i]]

I think that this would be the simplest solution possible.