How to replace duplicates with string and keep only first element in the list of lists?-CodePudding

my_list = [
     ['common1', '112', '4000'],
     ['common1', '11', '11'],
     ['common1', '33', '33'],
     ['common1', '33', '900'], 
     ['common2', '31', '400'],
     ['common2', '2', '2666']
]

I want to convert this list into

 [
    ['common1', '112', '4000'],
    ['', '11', '11'], 
    ['', '33', '33'],
    ['', '33', '900'], 
    ['common2', '31', '400'], 
    ['', '2', '2666']
 ]

Here what I want is replace the common1 with empty string '' and keep only the first value. Similarly for common2 value.

CodePudding user response：

You can try this:

def replace_duplicate(my_list):
    prev_val = ''

    for lst in my_list:
        if prev_val == lst[0]:
            lst[0] = ''
        else:
            prev_val = lst[0]

my_list = [
    ['common1', '112', '4000'],
    ['common1', '11', '11'],
    ['common1', '33', '33'],
    ['common1', '33', '900'], 
    ['common2', '31', '400'],
    ['common2', '2', '2666'],
    ['common3', '115', '5000'],
    ['common3', '12', '15'],
    ['common1', '222', '6000'],
    ['common1', '55', '66'],
    ['common1', '77', '99']
]

replace_duplicate(my_list)
print(my_list)

Output:

[
    ['common1', '112', '4000'],
    ['', '11', '11'],
    ['', '33', '33'],
    ['', '33', '900'],
    ['common2', '31', '400'],
    ['', '2', '2666'],
    ['common3', '115', '5000'],
    ['', '12', '15'],
    ['common1', '222', '6000'],
    ['', '55', '66'],
    ['', '77', '99']
]

CodePudding user response：

Here's a super simple and easy solution

def remove_sec_dups(data):
    seen = set()  # keep track of first seen values

    for sub in data:  # get sublists
        first = sub[0]  # get first item
        if first in seen:
            sub[0] = ''  # empty
        else:
            seen.add(first)  # add this to our seen list

remove_sec_dups(my_list)
print(my_list)

This outputs [['common1', '112', '4000'], ['', '11', '11'], ['', '33', '33'], ['', '33', '900'], ['common2', '31', '400'], ['', '2', '2666']]

CodePudding user response：

The following works for the general unsorted case, too:

seen = set()
for i, (head, *_) in enumerate(my_list):
    if head in seen:
        my_list[i][0] = ""
    seen.add(head)