How to delete a line with 20 characters in python?

Question

Python

Hello, there is a text file with a large number of lines, and some lines are repeated in it, but not completely, how can I make sure that lines in which less than 20 characters are deleted?

Answer 1

with open(file, 'r') as f:
    lines = f.readlines()

new = [line for line in lines if len(line) < 20]

Answer 2

Delete line by line from the file is "expensive", so we create a new file, into which we rewrite the lines from the old one, with the condition that if the line length is less than 20, then we ignore it.