Python | os.writev() method

OS module in Python provides functions for interacting with the operating system. OS comes under Python’s standard utility modules. This module provides a portable way of using operating system dependent functionality.

os.writev() method in Python is used to write the contents of specified buffers to the specified file descriptor. Here, buffers are sequence of mutable bytes-like objects. Buffers are processed in the specified order. The entire content of first buffer is written before proceeding to the second buffer, and so on.

A file descriptor is small integer value that corresponds to a file that has been opened by the current process. It is used to perform various lower level I/O operations like read, write, send etc.

Note: os.writev() method is only available on UNIX platforms.

Syntax: os.writev(fd, buffers)

fd: A file descriptor which is to be written.
buffers: A sequence of mutable bytes-like objects containing the data to be written to the specified file descriptor.

Return Type: This method returns an integer value which represents the number of bytes actually written.

Code: Use of os.writev() method to write contents of buffers to a file





# Python program to explain os.writev() method
# import os module
import os
# File path
path = "./file2.txt"
# Create a file and get the
# file descriptor associated 
# with it using method
fd =, os.O_CREAT | os.O_WRONLY)
# Bytes-like objects 
# the data to be written in the file
buffer1 = bytearray(b"GeeksForGeeks: ")
buffer2 = bytearray(b"A computer science portal ")
buffer3 = bytearray(b"for geeks")
# write the data contained in
# bytes-like objects
# to the file descriptor fd
# using os.writev() method
numBytes = os.writev(fd, [buffer1, buffer2, buffer3])
# print the content of file
with open(path) as f:
# Print the number of bytes actually written
print("Total Number of bytes actually written:", numBytes)



GeeksForGeeks: A computer science portal for geeks
Total Number of bytes actually written: 50
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