Python os.lseek()

The os module in Python provides functions for interacting with the operating system. os is a standard utility module in Python. This module provides a portable way to use operating system-related functionality.

Python The os.lseek() method sets the current position of the file descriptor fd to the given position pos and modifies the position by how.

Syntax: os.lseek(fd, pos, how)

Parameters:
fd: This is the file descriptor on which the seek is to be performed.
pos: This is the position in the file relative to the given argument how. It can accept three values:

• os.SEEK_SET or 0 to set the position relative to the beginning of the file
• os.SEEK_CUR or 1 to set the position relative to the current position
• os.SEEK_END or 2 to set the position relative to the end of the file

how: This is the reference point in the file. It also accepts three values:

• os.SEEK_SET or 0 sets the reference point to the beginning of the file
• os.SEEK_CUR or 1 sets the reference point to the current position
• os.SEEK_END or 2 sets the reference point to the end of the file.

Return value: This method does not return any value.

Example 1

Using the os.lseek() method to seek from the beginning of a file.

# Python program to explain the os.lseek() method.

# importing the os module

import os

# path

path = 'C:/Users/Rajnish/Desktop/testfile.txt'

# Open the file and get
# the file descriptor associated
# with it using os.open() method
fd = os.open(path, os.O_RDWR|os.O_CREAT)
  
# String to be written
s = 'GeeksforGeeks - A Computer Science portal'
  
# Convert the string to bytes
line = str.encode(s)
  
# Write the bytestring to the file
# associated with the file
# descriptor fd
os.write(fd, line)
  
# Seek the file from beginning
# using os.lseek() method
os.lseek(fd, 0, 0)
  
# Read the file
s = os.read(fd, 13)
  
# Print string
print(s)
  
# Close the file descriptor
os.close(fd)

Output:

b'GeeksforGeeks'

Example 2

Use the os.lseek() method to find files from a specific location

# Python program to explain os.lseek() method
        
# importing os module
import os
    
# path
path = 'C:/Users/Rajnish/Desktop/testfile.txt'
  
#Open the file and get
# the file descriptor associated
# with it using os.open() method
fd = os.open(path, os.O_RDWR|os.O_CREAT)
  
# String to be written
s = 'GeeksforGeeks'
  
# Convert the string to bytes
line = str.encode(s)
  
# Write the bytestring to the file
# associated with the file
# descriptor fd
os.write(fd, line)
  
  
# Seek the file after position '2'
# using os.lseek() method
os.lseek(fd, 2, 0)
  
# Read the file
s = os.read(fd, 11)
  
# Print string
print(s)
  
# Close the file descriptor
os.close(fd)

Output:

b'eksforGeeks'