Remove duplicates from a list, excluding start and end-CodePudding

Is there more pythonic way to remove all duplicate elements from a list, while keeping the first and last element?

lst = ["foo", "bar", "foobar", "foo", "barfoo", "foo"]

occurence = [i for i, e in enumerate(lst) if e == "foo"]

to_remove = occurence[1:-1]
for i in to_remove:
    del lst[i]

print(lst) # ['foo', 'bar', 'foobar', 'barfoo', 'foo']

Another approach which I like more.

for i, e in enumerate(lst[1:-1]): 
    if e == "foo": 
        del lst[i 1]

CodePudding user response：

You can construct a new list with your requirements using Python's set data structure and slicing like this:

lst = ["foo", "bar", "foobar", "foo", "barfoo", "foo"]
new_lst = [lst[0]]   list(set(lst[1:-1]))   [lst[-1]]

CodePudding user response：

Try below:

lst = ["foo", "bar", "foobar", "foo", "barfoo", "foo"]

first, last = lst[0], lst[-1]
seen = {first, last}
seen_add = seen.add

inner = (s for s in lst[1:-1] if not (s in seen or seen_add(s)))
result = [first, *inner, last]

Result:

['foo', 'bar', 'foobar', 'barfoo', 'foo']

CodePudding user response：

You can try this:

mylist = ["foo", "bar", "foobar", "foo", "barfoo", "foo"]
none_duplicated = list(dict.fromkeys(mylist))
print([mylist[0], *none_duplicated, mylist[-1]])

Actually, your question is not about to remove duplicates, but remove the occurrences of your first item in the list (assume first and last are the same). But if you want a more generic way, you will first try to get a list of none duplicated value, and then add your first and last.

CodePudding user response：

According to your example, it's necessary to remove the duplicates looking at the entire list and then adding the first and last elements:

lst = ["foo", "bar", "foobar", "foo", "barfoo", "foo"]

data = [lst[0],
        *set([w for w in lst if w not in [lst[0], lst[-1]]]),
        lst[-1]]
print(data)

Output:

['foo', 'bar', 'barfoo', 'foobar', 'foo']

CodePudding user response：

Use a slice-assignment and unpack/consume a filter?

lst = ["foo", "bar", "foobar", "foo", "barfoo", "foo"]

lst[1:-1] = filter(lambda x: x != "foo", lst[1:-1])
print(lst)

Output:

['foo', 'bar', 'foobar', 'barfoo', 'foo']