How to read lines from a file in python starting from the end

Question

I need to know how to read lines from a file in python so that I read the last line first and continue in that fashion until the cursor reach\'s the beginning of the file. A

Answer 1

A straightforward way is to first create a temporary reversed file, then reversing each line in this file.

import os, tempfile

def reverse_file(in_filename, fout, blocksize=1024):
    filesize = os.path.getsize(in_filename)
    fin = open(in_filename, 'rb')
    for i in range(filesize // blocksize, -1, -1):
        fin.seek(i * blocksize)
        data = fin.read(blocksize)
        fout.write(data[::-1])

def enumerate_reverse_lines(in_filename, blocksize=1024):
    fout = tempfile.TemporaryFile()
    reverse_file(in_filename, fout, blocksize=blocksize)
    fout.seek(0)
    for line in fout:
        yield line[::-1]

The above code will yield lines with newlines at the beginning instead of the end, and there is no attempt to handle DOS/Windows-style newlines (\r\n).