A quick introduction of Python sys.stdin and sys.stdout

A quick introduction of Python sys.stdin and sys.stdout


About sys.stdin and sys.stdout

sys.stdin and sys.stdout are file objects which are used by the interpreter for standard input and standard output. Data received by raw_input comes from stdin, which is normally connects to the keyboard. stdin can be redirected so that input instead comes from a file. This can be very useful for automating scripts.

About sys.stdout.write() and print()

When you call the print(obj) function, it actually call the sys.stdout.write(obj + '\n') like below:

import sys
sys.stdout.write("hello" + "\n")

About sys.stdin.readline() and input()

The input() function first takes the input from the user and then evaluates the expression. Python automatically identifies whether the user entered a string or a integer or a list.


  • Whatever you enter as input, input function converts it into a string.

The sys.stdin.readline() reads the escape character entered by the user, like below

import sys

name = sys.stdin.readline()

num = sys.stdin.readline(2)


# Input Alison
# Input 1234

Differences between input() and sys.stdin.readline() functions:

input() sys.stdin.readline()
The input takes input from the user but doesn’t 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