why is the output of the code coming as "Time's up!ning: 1" and not "Time's up!" in python jupyter notebook?

Question

import time

# Print a countdown using carriage return
def countdown():
    for i in range(5, 0, -1):
        print(f"Time remaining: {i}", end='\r')

    print("Time's up!")

# Call the countdown function
countdown()

by using "\r"(carriage return) the output must have been the last print statement "Time's up!" but the output coming is "Time's up!ning: 1"

Answer 1

Here’s a breakdown of what’s happening:

1. Carriage Return \r: This character moves the cursor back to the start of the current line in the console. It doesn't erase the content of the line but simply allows new text to overwrite the old one.

2. Line Overwriting: In your countdown loop, each new "Time remaining: X" message overwrites the previous one because of \r. However, if the new message is shorter than the previous one, it doesn't completely erase the old message.

3. Final Print Statement: When you print "Time's up!", it overwrites the beginning of the last "Time remaining: 1" message. Since "Time's up!" is shorter than "Time remaining: 1", the remaining characters ("ning: 1") from the previous message are not overwritten and remain visible.

This results in the concatenated output "Time's up!ning: 1".

To fix this and ensure that Time's up! cleanly overwrites the previous line, you can pad it with spaces to ensure it's as long as the longest message it's overwriting:

import time

def countdown():
    for i in range(5, 0, -1):
        print(f"Time remaining: {i} ", end='\r')
        time.sleep(1)  # Adding a small delay to see the countdown

    print("Time's up!      ")  # Pad with spaces

countdown()

Answer 2

Carriage return '\r' returns the cursor to the beginning of the line, so your output it re-printing itself on top of itself each time. That extra 'ning: 1' is the remainder from the last "Time remaining: 1" from your countdown.

Your code will show all the rows of the countdown if you delete the 'end' parameter, which will by default cause the print to use a new line '\n' instead.

More details (historical and otherwise) in this thread: Difference between \n and \r?

Fixed code:

import time
# Print a countdown using carriage return
def countdown():
    for i in range(5, 0, -1):
        print(f"Time remaining: {i}")

    print("Time's up!")

# Call the countdown function
countdown()