Examples of seven ways Python removes duplicate elements from a list

l1 = [1, 1, 2, 2, 3, 3, 3, 3, 6, 6, 5, 5, 2, 2]

for el in l1:
    if (el) > 1:
        (el)
print(l1)# will be missed because when an element is deleted, the following element is moved forward, causing the immediately following element to be skipped.

l1 = [1, 1, 2, 2, 3, 3, 3, 3, 6, 6, 5, 5, 2, 2]
for el in range(len(l1)):  # At this point, len(l1) has been determined, and will not change as l1 changes.
    if (l1[el]) > 1:
        (l1[el])
print(l1)  # will report an error, because the deletion of the element causes the length of l1 to become shorter, but for traversal of the previous index length, will cause the index to exceed the range and report an error

l1 = [1, 1, 2, 2, 3, 3, 3, 3, 6, 6, 5, 5, 2, 2]
for el in l1[:]:
    if (el) > 1:
        (el) # There's no problem, you can de-duplicate, but you can't preserve the original order #
print(l1)   

l1 = [1, 1, 2, 2, 3, 3, 3, 3, 6, 6, 5, 5, 2, 2]
lst = []
for el in l1:
    if (el) < 1:
        (el)
print(lst)   # No problem, also preserves the original order, but creates a new list.

l1 = [1, 1, 2, 2, 3, 3, 3, 3, 6, 6, 5, 5, 2, 2]
for el in range(len(l1)-1, -1, -1):
    if (l1[el]) > 1:
        (el)  # No problem, and the original order is preserved #
        # (l1[el]) # No problem, but you can't keep the original order.
        # del l1[el] # This will keep the original order, you can think about why.
print(l1)   

l1 = [1, 1, 2, 2, 3, 3, 3, 3, 6, 6, 5, 5, 2, 2]
def set_lst(lst):
    for el in lst:
        if (el) > 1:
            (el)
            set_lst(lst)    # Each time a new function is opened, determine the list after the last time an element was deleted.
    else:  # Until the end, the elements in the list are all one, run else
        return lst
print(set_lst(l1))  # Since the deletion starts from the front, the original order is not preserved.
'''
[1, 1, 2, 2, 3, 3, 3, 3, 6, 6, 5, 5, 2, 2]
[1, 2, 2, 3, 3, 3, 3, 6, 6, 5, 5, 2, 2]
[1, 2, 3, 3, 3, 3, 6, 6, 5, 5, 2, 2]
[1, 3, 3, 3, 3, 6, 6, 5, 5, 2, 2]
[1, 3, 3, 3, 6, 6, 5, 5, 2, 2]
[1, 3, 3, 6, 6, 5, 5, 2, 2]
[1, 3, 6, 6, 5, 5, 2, 2]
[1, 3, 6, 5, 5, 2, 2]
[1, 3, 6, 5, 2, 2]
[1, 3, 6, 5, 2]   return lst = [1, 3, 6, 5, 2]
'''

l1 = [1, 1, 2, 2, 3, 3, 3, 3, 6, 6, 5, 5, 2, 2]
lst = list(set(l1))
print(lst)