Introduction

The os library in Python serves as a cornerstone for interacting with the operating system, providing functions for file and directory manipulation, process management, environment variables, and more. This chapter delves into the myriad capabilities of the os module and demonstrates its utility through practical examples.

Topics

File and directory operations
Process management
Environment variables manipulation

File and Directory Operations

The os module offers a plethora of functions for performing file and directory operations, facilitating tasks such as file creation, deletion, renaming, and directory navigation.

Checks for the existence of a file

import os

# Check if a file exists
file_path = "example.txt"
if os.path.exists(file_path):
    print("File exists.")
else:
    print("File does not exist.")

Output:

File does not exist.

Creates a new folder

import os

# Create a directory
directory_path = "example_directory"
os.mkdir(path=directory_path)
print("Directory created.")

Output:

Directory created.

Renames a file

import os

# Rename a file
file_path = "example.txt"
new_file_path = "new_example.txt"
os.rename(file_path, new_file_path)
print("File renamed.")

Output:

File renamed.

Lists the files found within a directory

import os

# List files in a directory
directory_path = "example_directory"
files = os.listdir(path=directory_path)
print("Files in directory:", files)

Output:

Files in directory: ['example.txt']

Deletes a directory as long as it is empty

import os

# Remove a directory
directory_path = "example_directory"
os.rmdir(path=directory_path)
print("Directory removed.")

Output:

Directory removed.

Process Management

With the os module, you can interact with processes, including launching new processes, obtaining process IDs, and managing process attributes.

import os

# Launch a new process
os.system("ls -l")

# Get the process ID of the current process
pid = os.getpid()
print("Process ID:", pid)

# Get the parent process ID
ppid = os.getppid()
print("Parent Process ID:", ppid)

Output:

total 96
-rw-r--r--@ 1 tlayach  staff      0 Feb 26 00:03 example.txt

Environment Variables Manipulation

The os module enables manipulation of environment variables, allowing you to retrieve, set, and unset environment variables.

import os

# Get value of an environment variable
python_path = os.getenv("PYTHONPATH")
print("PYTHONPATH:", python_path)

# Set an environment variable
os.environ["NEW_VARIABLE"] = "new_value"
print("NEW_VARIABLE set.")

# Unset an environment variable
os.environ.pop("NEW_VARIABLE", None)
print("NEW_VARIABLE unset.")

Output:

PYTHONPATH: /Users/...
NEW_VARIABLE set.
NEW_VARIABLE unset.

Conclusion

The os library in Python serves as a versatile toolkit for interacting with the operating system, empowering developers to perform a wide range of file and directory operations, manage processes, and manipulate environment variables seamlessly.