read the last line of a file in python

Question

I have a two requirements .

First Requirement-I want to read the last line of a file and assign the last value to a variable in python.

Answer 1

A simple solution, which doesn't require storing the entire file in memory (e.g with file.readlines() or an equivalent construct):

with open('filename.txt') as f:
    for line in f:
        pass
    last_line = line

For large files it would be more efficient to seek to the end of the file, and move backwards to find a newline, e.g.:

import os

with open('filename.txt', 'rb') as f:
    f.seek(-2, os.SEEK_END)
    while f.read(1) != b'\n':
        f.seek(-2, os.SEEK_CUR)
    last_line = f.readline().decode()

Note that the file has to be opened in binary mode, otherwise, it will be impossible to seek from the end.