The os Module

The os module in Python provides functions to interact with the operating system. It allows you to perform tasks like handling directories, working with file paths, and accessing system information.

Key Features of os

1. Working with Directories

Get the Current Working Directory

import os

print(os.getcwd())  # Output: Current working directory

Change the Current Working Directory

os.chdir("/path/to/directory")
print(os.getcwd())  # Output: Updated working directory

Create a Directory

os.mkdir("new_folder")  # Creates a single directory

Create Nested Directories

os.makedirs("parent_folder/child_folder")  # Creates directories recursively

Remove a Directory

os.rmdir("new_folder")  # Removes an empty directory

Remove Nested Directories

os.removedirs("parent_folder/child_folder")  # Removes directories recursively

2. Working with Files

Check if a File or Directory Exists

print(os.path.exists("example.txt"))  # Output: True or False

Rename a File

os.rename("old_name.txt", "new_name.txt")

Remove a File

os.remove("example.txt")

3. Path Operations with os.path

The os.path module provides functions to work with file paths.

Join Paths

path = os.path.join("folder", "subfolder", "file.txt")
print(path)  # Output: folder/subfolder/file.txt

Split a Path

directory, file = os.path.split("/folder/file.txt")
print(directory)  # Output: /folder
print(file)       # Output: file.txt

Get File Extension

_, extension = os.path.splitext("file.txt")
print(extension)  # Output: .txt

4. System Information

Get the Operating System Name

print(os.name)  # Output: 'posix' (Linux/Mac), 'nt' (Windows)

Get Environment Variables

print(os.environ)  # Dictionary of environment variables
print(os.environ.get("PATH"))  # Access a specific environment variable

Execute a System Command

os.system("ls")  # Runs the `ls` command (Unix) or `dir` (Windows)

5. Traversing the File System

Walk Through a Directory Tree

The os.walk() function generates the file names in a directory tree.

for root, dirs, files in os.walk("example_folder"):
    print("Root:", root)
    print("Directories:", dirs)
    print("Files:", files)

6. File Permissions

Change Permissions of a File

os.chmod("example.txt", 0o644)  # Change file permissions

Get File Metadata

info = os.stat("example.txt")
print(info.st_size)  # File size in bytes
print(info.st_mtime)  # Last modified time

Practical Example

Script to Organize Files by Extension

import os

def organize_files(directory):
    os.chdir(directory)
    for file in os.listdir():
        if os.path.isfile(file):
            ext = os.path.splitext(file)[1][1:]  # Get the extension without the dot
            if not os.path.exists(ext):
                os.mkdir(ext)
            os.rename(file, os.path.join(ext, file))

organize_files("downloads_folder")

This script moves files into subfolders based on their extensions.

Best Practices

1. Error Handling:
   • Always handle exceptions when performing file or directory operations.

     try:
       os.remove("nonexistent_file.txt")
     except FileNotFoundError:
       print("File not found!")
     

2. Use os.path for Portability:
   • Avoid hardcoding file paths. Use os.path functions to make your code work across different operating systems.
3. Clean Up Resources:
   • Ensure files and directories are closed or properly cleaned up after operations.

Practice Exercises

1. Directory Management:
   • Write a script that creates a nested directory structure and then removes it.
2. File Organization:
   • Write a script that organizes all files in a directory into subdirectories based on their extensions.
3. System Commands:
   • Use os.system() to execute a system command and capture its output.

The os module is a powerful tool for managing the file system and interacting with the operating system in a Pythonic way.