sys.stdout.write in Python

Last Updated : 11 Apr, 2025

sys.stdout.write() is a built-in Python method that writes output directly to the console without automatically adding a newline (\n). It is part of the sys module and requires import sys before use.

Unlike print(), it does not insert spaces between multiple arguments, allowing precise control over text formatting. It returns the number of characters written instead of None. Example:

Python

import sys  sys.stdout.write("Hello, ") sys.stdout.write("World!")  res = sys.stdout.write("Gfg")  # Capturing return value print("\nReturn Value:", res)

Output

Hello, World!Gfg Return Value: 3

Explanation:

sys.stdout.write(“Hello, “) writes “Hello, ” without moving to a new line.
sys.stdout.write(“World!”) continues on the same line.
sys.stdout.write(“Gfg”) appends “Gfg” and returns 3, the number of characters written. Finally, print(“\nReturn Value:”, res) moves to a new line.

Syntax of sys.stdout.write

sys.stdout.write(“string”)

Parameters:

string: The text that will be written to the standard output.

Return Value: It returns the number of characters written. In interactive mode, this value may be displayed because the interpreter echoes function return values.

Examples of sys.stdout.write

Example 1: Use sys.stdout.write() in a loop

This example demonstrate how to print elements of a list on the same line and then on separate lines using sys.stdout.

Python

import sys  var = sys.stdout  s = ['Python', 'is', 'awesome']  # Print on the same line for e in s:     var.write(e + ' ') var.write('\n')  # New line  # Print each element on a new line for e in s:     var.write(e + '\n')

Output

Python is awesome  Python is awesome

Explanation: sys.stdout.write() prints list elements on the same line using a space and then on separate lines with \n. This avoids automatic spaces or newlines from print().

Example 2: Redirect output to a file

A useful feature of sys.stdout is that it can be reassigned, allowing us to redirect output to a file instead of displaying it on the console. This is particularly helpful for logging and storing program results.

Python

import sys  with open('output.txt', 'w') as file:     sys.stdout = file  # Redirect output to file     print('Geeks for geeks')  sys.stdout = sys.__stdout__  # Restore stdout

Output

output.txt file

Explanation:

Temporarily redirect sys.stdout to a file object.
Any standard output (like print()) is then written to the file.
After writing, we restore the original sys.stdout to resume console output.

Example 3: Create a dynamic countdown

This example shows how to use sys.stdout.write() to dynamically update text on the same line, it’s useful for countdowns or progress bars.

Python

import sys import time  for i in range(5, 0, -1):     sys.stdout.write(f'\rCountdown: {i} ')       sys.stdout.flush()     time.sleep(1)  sys.stdout.write("\nTime's up!\n")  # Use double quotes to avoid conflict with the apostrophe

Output

dynamic countdown

Explanation:

\r (carriage return) moves the cursor to the start of the line.
sys.stdout.flush() ensures the text is immediately printed.
time.sleep(1) adds a one-second delay between updates.
Finally, we print “Time’s up!” on a new line.

To read about more Python’s built in methods, refer to Python’s Built In Methods

Difference between print() and sys.stdout.write()

Understanding this difference is important for precise output control, especially in scenarios like dynamic console updates, logging or writing to files. It helps in optimizing performance, avoiding unnecessary formatting and ensuring the desired output structure in various programming tasks.

Feature	print()	sys.stdout.write()
Auto newline	Yes (print() adds \n by default)	No (must manually add \n if needed)
Output Formatting	Supports sep and end parameters	No additional formatting options
Returns	None	Number of characters written

Python | Testing Output to stdout

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sys.stdout.write in Python

Syntax of sys.stdout.write

Examples of sys.stdout.write

Example 1: Use sys.stdout.write() in a loop

Example 2: Redirect output to a file

Example 3: Create a dynamic countdown

Difference between print() and sys.stdout.write()

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