import sys

sys.stdin and sys.stdout

sys.stdin and sys.stdout are useful when creating an interactive session. sys.stdin is a file object and we can loop it through its iterator:

import sys

for line in sys.stdin:
    if line.strip() == 'exit':
        break
    sys.stdout.write(f">> {line}")

Status Bar

Build a status bar using sys.stdout.write. The \r moves the cursor to the beginning of the line:

import time
import sys

for i in range(101):
    time.sleep(0.1)
    sys.stdout.write(f"{i} [{'#' * i}{'.' * (100 - i)}]\r")
sys.stdout.write('\n')

input() vs. sys.stdin.readline()

input()	sys.stdin.readline()
The input takes input from the user but does not read escape character.	The readline() also takes input from the user but also reads the escape character.
It has a prompt that represents the default value before the user input.	Readline has a parameter named size, Which is a non-negative number, it actually defines the bytes to be read.

Reference

What does sys.stdin read?Stack Overflow

What does sys.stdin read?

Difference between input() and sys.stdin.readline() - GeeksforGeeksGeeksforGeeks

Difference between input() and sys.stdin.readline() - GeeksforGeeks