Create unique list (my def)

Question

Im not sure why my code does not do what I want (I want to return a list of unique items)

B = ["blue", "blue", "red",   "green", "red",  "blue", "yellow", "green", "blue", "red"]
def makeUnique(list):
    unique = []
    for i in range(0, len(list)):
        if list[i] not in unique:
            unique.append(item)
    return unique
print makeUnique(B)

It returns

['red', 'red', 'red', 'red', 'red', 'red', 'red']

Edit: idents might be incorrect, when pasting some was missing, so its not a ident error or sth

Searching other questions already answered is often the best way to find an effective, tested solution. One line command: https://stackoverflow.com/questions/12897374/get-unique-values-from-a-list-in-python — Douglas, Jun 21 '17 at 17:35
Or change your loop to `for item in list:` and use `item` rather that `list[i]`. On a side note, it's bad practice to use builtins as variable names. — zondo, Jun 21 '17 at 17:35

score 3 · Answer 1 · answered Jun 21 '17 at 17:32

3

Maurice Meyer already found the bug in your code, but in general, this algorithm is not optimal - to find unique values in a list, just do:

newlist = list(set(oldlist))

answered Jun 21 '17 at 17:32

Błotosmętek

12,717
19
29

`list(set(...))` loses order – inspectorG4dget Jun 21 '17 at 17:32
@inspectorG4dget keeping order wasn't explicitly specified as a requirement, but you're right, it is reasonable to want that. – Błotosmętek Jun 21 '17 at 17:34
1

Or, `>>> np.unique(x); array(['blue', 'green', 'red', 'yellow'], dtype='|S6')` If you're a badass. – cs95 Jun 21 '17 at 17:37

score 2 · Answer 2 · answered Jun 21 '17 at 17:32

You're appending item, which doesn't exist in the context of the function. You have to append the item you're iterating over:

B = ["blue", "blue", "red",   "green", "red",  "blue", "yellow", "green", "blue", "red"]

def makeUnique(list):
    unique = []
    for i in range(0, len(list)):
        if list[i] not in unique:
            unique.append(list[i])
    return unique


print(makeUnique(B))  # ['blue', 'red', 'green', 'yellow']

Create unique list (my def)

2 Answers2