Python OS Module

The os module in Python is a standard library module that allows you to interact with the operating system. It enables you to perform operating system-dependent tasks, such as file and directory manipulation, process management, and accessing environment variables.

1. Accessing the os Module

To use the os module, you first need to import it:

import os

2. Key Functionalities of the os Module

File and Directory Operations

1. Working with the Current Working Directory

• os.getcwd(): Returns the current working directory.

cwd = os.getcwd()
print("Current Directory:", cwd)

• os.chdir(path): Changes the current working directory to the specified path.

os.chdir("/path/to/directory")

2. Creating and Removing Directories

• os.mkdir(path): Creates a single directory.

os.mkdir("new_folder")

• os.makedirs(path): Creates directories recursively.

os.makedirs("parent_folder/child_folder")

• os.rmdir(path): Removes an empty directory.

os.rmdir("new_folder")

• os.removedirs(path): Removes directories recursively.

os.removedirs("parent_folder/child_folder")

3. Listing Files and Directories

• os.listdir(path="."): Lists all files and directories in the given path.

items = os.listdir(".")
print(items)

4. Renaming and Deleting Files

• os.rename(src, dst): Renames a file or directory.

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

• os.remove(path): Deletes a file.

os.remove("file.txt")

Environment Variables

1. Getting and Setting Environment Variables

• os.environ: A dictionary-like object containing the environment variables.

print(os.environ["PATH"])

• os.environ["NEW_VAR"] = "value": Sets a new environment variable.

os.environ["MY_VAR"] = "123"
print(os.environ["MY_VAR"])

2. Getting a Specific Environment Variable

• os.getenv(key, default=None): Gets the value of an environment variable.

home_dir = os.getenv("HOME")
print(home_dir)

Path Manipulations

1. Checking Existence and Properties

• os.path.exists(path): Checks if a path exists.

exists = os.path.exists("file.txt")
print(exists)

• os.path.isdir(path): Checks if a path is a directory.
• os.path.isfile(path): Checks if a path is a file.

2. Joining and Splitting Paths

• os.path.join(path1, path2): Joins two or more paths.

full_path = os.path.join("folder", "file.txt")
print(full_path)

• os.path.split(path): Splits a path into head and tail.

head, tail = os.path.split("/path/to/file.txt")
print("Head:", head)
print("Tail:", tail)

3. Getting File Information

• os.path.getsize(path): Gets the size of a file in bytes.

size = os.path.getsize("file.txt")
print("File Size:", size, "bytes")

Process Management

1. Getting Process Information

• os.getpid(): Gets the current process ID.

print("Process ID:", os.getpid())

• os.getppid(): Gets the parent process ID.

print("Parent Process ID:", os.getppid())

2. Starting New Processes

• os.system(command): Executes a system command in a subshell.

os.system("ls")

Platform Information

• os.name: Returns the name of the operating system-dependent module imported.

print(os.name) # 'posix' for Unix-like, 'nt' for Windows

• os.uname(): Provides system information (Unix-like systems only).

print(os.uname())

Miscellaneous

1. Changing Permissions

• os.chmod(path, mode): Changes the mode (permissions) of a file or directory.

os.chmod("file.txt", 0o644)

2. Walking a Directory Tree

• os.walk(top, topdown=True): Generates the file names in a directory tree.

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

Example: Combining Multiple Functions

import os

# Get current working directory
cwd = os.getcwd()
print("Current Directory:", cwd)

# Create a new directory
os.mkdir("test_dir")

# Change to the new directory
os.chdir("test_dir")
print("Changed Directory:", os.getcwd())

# Create a file in the directory
with open("example.txt", "w") as f:
    f.write("Hello, world!")

# List contents
print("Directory Contents:", os.listdir("."))

# Clean up
os.remove("example.txt")
os.chdir("..")
os.rmdir("test_dir")

The os module is a very important tool for tasks that involve interacting with the file system and the operating system.