Remove item from list based on the next item in same list

Question

I just started learning python and here I have a sorted list of protein sequences (total 59,000 sequences) and some of them overlap. I have made a toy list here for example:

Answer 1

You could use groupby() and max() to help here:

from itertools import groupby

with open('toy.txt') as f_input:
    for key, group in groupby(f_input, lambda x: x[:2]):
        print(max(group, key=lambda x: len(x)).strip())

This would display:

ABCDEFGHIJKLMNO
CEST
DBTSFDEO
EOEUDNBNUW
EAEUDNBNUW
FGH

groupby() works by returning a list of matching items based on a function, in this case consecutive lines with the same first 2 characters. The max() function then takes this list and returns the list item with the longest length.