How do I make a function that returns a list of unique strings, given a list of strings with duplicates? [duplicate]

Question

This question already has answers here:

Removing duplicates in lists (57 answers)

Closed 9 years ago.

This is a piece of homework for my programming course. We are asked to make a function that accepts a list of strings as a parameter, and then returns the same list of strings but without duplicates.
e.g:

>>> unique_list(['dog','cat','dog','fish'])
['dog','cat','fish']

Any information regarding the matter would be greatly appreciated.

Answer 1

Use the following code:

>>> def unique_list(mylist):
...     copy = []
...     for k in mylist:
...             if k not in copy:
...                     copy.append(k)
...     return copy
... 
>>> unique_list([1])
[1]
>>> unique_list([1, 1])
[1]
>>> unique_list([1, 1, 2])
[1, 2]
>>> unique_list([1, 3, 1, 2])
[1, 3, 2]
>>> unique_list(['dog','cat','dog','fish'])
['dog', 'cat', 'fish']

The for loop loops over every item in mylist. If the item is already in copy, it does nothing. Otherwise, it adds the item to copy. At the end, we return the 'unduplicatified' version of mylist, stored in copy.

Or a one-liner would be:

>>> def unique_list(mylist):
...     return list(set(mylist))
... 
>>> unique_list([1])
[1]
>>> unique_list([1, 1])
[1]
>>> unique_list([1, 1, 2])
[1, 2]
>>> unique_list([1, 3, 1, 2])
[1, 2, 3]
>>> unique_list(['dog','cat','dog','fish'])
['fish', 'dog', 'cat'] 

Answer 2

def unique_list(subject):
    return list(set(subject))

This is what you can write in python 3.3