Python: Marking duplicates in list

Question

I have an unordered python list, what I want is to create 2nd list which will tell either the values in the first list are duplicate or unique. For duplicates i have to mark them as duplicate1, duplicate2 and so on. I will create a dictionary from these lists and later on these will be use in pandas dataframe.

I am stuck on logic of 2nd_list, could someone please help.

first_List = ['a',  'b', 'c', 'a', 'd', 'c']

EXPECTED OUTPUT:

second_List = ['dup1', 'unique', 'dup1', 'dup2', 'unique', 'dup2']

You made a little typo error in 2nd list. You show "a" as unique and "d" as dup2. — Rishabh Semwal
– Rishabh Semwal, Commented May 21, 2021 at 11:45

ThePyGuy · Accepted Answer · 2021-05-21 12:01:59Z

You can iterate the list by index, and for list value at given index, check if it is duplicate or not (isDuplicate) boolean is created in the code below, if it is a duplicate entry, then count how many times the current value appeared in the list for the given index and append the string to the second_List

second_List = []
for i in range(len(first_List)):
    isDuplicate = first_List.count(first_List[i]) > 1
    if isDuplicate:
        count = first_List[:i+1].count(first_List[i])
        second_List.append(f'dup{count}')
    else:
        second_List.append('unique')

OUTPUT:

['dup1', 'unique', 'dup1', 'dup2', 'unique', 'dup2']

Here is the equivalent List-Comprehension as well, if you are interested!

>>> [f'dup{first_List[:i+1].count(first_List[i])}' 
... if first_List.count(first_List[i]) > 1 
... else 'unique'
... for i in range(len(first_List))]

['dup1', 'unique', 'dup1', 'dup2', 'unique', 'dup2']

handowl · Accepted Answer · 2021-05-21 12:29:31Z

To be short

first_List = ['a',  'b', 'c', 'a', 'd', 'c']

d = {i:'' for i in first_List if first_List.count(i) > 1}
second_List = ['unique' if i not in d.keys() else f'dup{list(d.keys()).index(i)+1}' for i in first_List]

It works fine.

This is the same as

d = {i:'' for i in first_List if first_List.count(i) > 1}
second_List = list()
for i in first_List:
    text = 'unique' if i not in d.keys() else f'dup{list(d.keys()).index(i)+1}'
    second_List.append(text)

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