Python Program to Reverse the Content of a File using Stack

Given a file, the task is to print as well as store the lines of that file in reverse order using Stack.
Examples:

Input :
I am
new to this
world of
Python.

Output :
Python.
world of
new to this
I am


Input :
1
2
3
4
5
Output :
5
4
3
2
1

Approach:

• Create an empty stack. 
  
• One by one push every line of the file to the stack. 
  
• One by one pop each line from the stack and put them back to the file. 
  

Below is the implementation.
Input File:

Python3

# Python3 code to reverse the lines
# of a file using Stack.


# Creating Stack class (LIFO rule)
class Stack:

    def __init__(self):

        # Creating an empty stack
        self._arr = []

    # Creating push() method.
    def push(self, val):
        self._arr.append(val)

    def is_empty(self):

        # Returns True if empty
        return len(self._arr) == 0

    # Creating Pop method.
    def pop(self):

        if self.is_empty():
            print("Stack is empty")
            return

        return self._arr.pop()

# Creating a function which will reverse
# the lines of a file and Overwrites the
# given file with its contents line-by-line
# reversed
def reverse_file(filename):

    S = Stack()
    original = open(filename)

    for line in original:
        S.push(line.rstrip("\n"))

    original.close()


    output = open(filename, 'w')

    while not S.is_empty():
        output.write(S.pop()+"\n")

    output.close()


# Driver Code
filename = "GFG.txt"

# Calling the reverse_file function
reverse_file(filename)

# Now reading the content of the file
with open(filename) as file:
        for f in file.readlines():
            print(f, end ="")

Output:

This is a World of Geeks.
Welcome to GeeksforGeeks.

 Time complexity: O(n), where n is the number of lines in the file.

Auxiliary space: O(n), where n is the number of lines in the file.