How can I write a list without duplicate with only for, if and boolean

Question

My professor gave me an exercise where I write a function that returns a list without the duplicate to the old list. This is the code but I don\'t know how to write the meth

Answer 1

If you need to eliminate duplicates AND preserve order you can do this:

def distinct(lst):
    seen = set()
    for item in lst:
        if item not in seen:
            yield item
            seen.add(item)

---

a = [1,3,1,2,6]

print(list(distinct(a)))

[1,3,2,6]

---

b = ['a','ab','a','ab']

print(list(distinct(b)))

['a', 'ab']

See a demo here: https://ideone.com/a2khCg

Answer 2

def distinct(lst):
    dlst = []
    for val in lst:
        if val not in dlst:
            dlst.append(val)
    return dlst

Answer 3

If order isn't important, you can cast it to a set, then back to a list

def distinct(lst):
    return list(set(lst))

Answer 4

Is this considered cheating?

>>> distinct = lambda lst: list(set(lst))
>>> distinct([1,3,1,2,6])
[1, 2, 3, 6]
>>> distinct(['a','ab','a','ab'])
['a', 'ab']

Answer 5

There are Excellent Solutions That I Already Applied. But my professor said us that we don't must use the methods of the list. Has anyone else got any more thoughts?