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Python Exercise Lists

Answer for Python File Input Output Exercise 3

3. Write a python program to read the last n lines of file, a.txt.

The output is:

Original file a.txt:
Welcome to
www.freelearningpoints.com

Expected Answer:
www.freelearningpoints.com

Sample Answer:

import sys
import os
def read_file(file_name,last_lines):
        buf_size = 8192
        file_size = os.stat(file_name).st_size
        iter = 0
        with open(file_name) as f:
                if buf_size > file_size:
                        buf_size = file_size-1
                        data = []
                        while True:
                                iter +=1
                                f.seek(file_size-buf_size*iter)
                                data.extend(f.readlines())
                                if len(data) >= last_lines or f.tell() == 0:
                                        print(''.join(data[-last_lines:]))
                                        break

read_file('a.txt', 1)

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