Question

Possible Duplicates:
How do you remove duplicates from a list in Python whilst preserving order?
In Python, what is the fastest algorithm for removing duplicates from a list so that all elements are unique while preserving order?

I was wondering if there was a function which does the following:

Take a list as an argument:

list = [ 3 , 5 , 6 , 4 , 6 , 2 , 7 , 6 , 5 , 3 ]

and deletes all the repeats in the list to obtain:

list = [ 3 , 5 , 6 , 4 , 2 , 7 ]

I know you can convert it into a dictionary and use the fact that dictionaries cannot have repeats but I was wondering if there was a better way of doing it.

Thanks

Answer 1

Please see the Python documentation for three ways to accomplish this. The following is copied from that site. Replace the example ‘mylist’ with your variable name (‘list’).

First Example: If you don’t mind reordering the list, sort it and then scan from the end of the list, deleting duplicates as you go:

if mylist:
    mylist.sort()
    last = mylist[-1]
    for i in range(len(mylist)-2, -1, -1):
        if last == mylist[i]:
            del mylist[i]
        else:
            last = mylist[i]

Second Example: If all elements of the list may be used as dictionary keys (i.e. they are all hashable) this is often faster:

d = {}
for x in mylist:
    d[x] = 1
mylist = list(d.keys())

Third Example: In Python 2.5 and later:

mylist = list(set(mylist))