Working with the Operating System

Learning Outcomes

Using the Path() function from the pathlib module to create proper paths for your operating system.
Using the Path.glob() function to find directory names with a specific match pattern.
Go over basic commands of the os module.
Learn how to copy, move, rename, and delete files with the shutil module.

Differences between Operating Systems

Operating systems use different path separators when working with files. Path separators are characters that separate individual paths. For example, a path in Windows looks like C:\\Users\\Joe\\data.txt, while in Linux it looks like /home/joe/data.txt'. This is because Windows uses backslashes and macOS + Linux use forward slashes as their path separators. Windows uses two backslashes to avoid escape characters. Therefore, when writing programs that work on multiple operating systems, we will use the Path() function from the pathlib module so that we don't run into errors.

Pathlib module and the Path Object

When working with Windows, the Path(path) returns a WindowsPath object, and in macOS + Linux, it returns a PosixPath object. Using the str() method on these objects yields the path string, which automatically happens when using the print() function as shown below.

>>> from pathlib import Path
>>> Path("users", "joe", "data.txt")
PosixPath('users/joe/data.txt')

>>> print(Path("users", "joe", "data.txt"))
'users/joe/data.txt'

To find our current directory, we can call the Path.cwd() function and to find our home directory we can use Path.home().

Given a path object, path = Path('C:\Users\Joe\data.txt'), we can run common commands such as:

path.is_absolute() returns whether the Path object is an absolute path.
absolute_path / Path(relative_path) returns an absolute path for a relative path. The relative_path can be relative to any absolute_path such as Path.cwd() and Path.home().
path.exists() returns whether the path is a valid path.
path.is_file() returns whether the path is of type file.
path.is_dir() returns whether the path is a directory.

We will be using the windows path C:\\Users\\Joe\\data.txt as an example to show how we can break up a path into its components as shown below:

p.anchor root folder of the file system (C:)
p.parent returns a Path object which includes all folders before the current file (C:\Users\Joe)
p.name returns the file name with the extension (data.txt)
p.stem return the file name without the extension (data)
p.suffix returns the extension of the path (.txt)

Glob Patterns with the pathlib Module

We can use glob patterns, which are similar to using regex, to find specific files. Since using the glob() method yields a generator object, we will be using the list() function when printing them out.

list(path.glob('*')) will return all paths.
list(path.glob('*.py')) returns all python files.
list(path.glob('*.??)) return all files with a 2-character extension. The ? represents any single character.

os Module

The os module lets us interact with our operating system by navigating files, getting file information, modifying environment variables, and more. Unlike the way that the pathlib module lets us use paths like objects, the os module represents paths as strings. We recommend using the pathlib module due to its ease of use, but we'll still go over some aspects of the os module.

Following are some common commands:

os.getcwd() gets the current working directory.
os.chdir(path) change directory to an absolute path.
os.listdir() lists files and folders under the current folder.
os.mkdir(file_name) create directory.
os.makedirs(nested_file_name) creates a directory with the ability to make subdirectories.
os.rmdir(file_name) deletes exact directory.
os.removedirs(nested_file_name) deletes directory down file tree.
os.stat(file_name) returns information about a file, such as its size, last modified, and more.
os.rename(current_file_name, new_file_name) changes the name of a file.
os.walk(path) returns a tuple of (current path, directories, files) of traversing the paths in your system starting at a given path.
os.environ.get(env_variable) allows you to retrieve values of your environment variables.

os.path Module

We can also use commands on paths

os.path.join(path, file_name) returns a joint path.
os.path.basename(path) returns the base name of your path.
os.path.dirname(path) returns the path of the directory name.
os.path.split(path) returns the directory name and base name of the path.
os.path.exists(path) returns whether a file exists on your file system.
os.path.isdir(path) returns whether or not your path is a directory.
os.path.isFile(path) returns whether your path is a file or not.
os.path.splitext(path) returns the path and its extension.

shutil Module

The shutil module provides the capability to copy, move, rename, and delete with both string paths and Path objects.

Running the command shutil.copy(source, destination) copies a file at the source path and pasts it at the path destination. If the destination is a folder, the file will be placed in that folder. If instead, the destination is a file, the file will be replaced by the source file.

If we'd like to copy an entire folder(including its subfolders), we can use the shutil.copytree(source, destination) method. Running the method will return the string of the copied folder path.

We can move one file or folder to another folder using the shutil.move(source, destination) function. We can rename a file by moving the file to a new file location like so:

shutil.move("C:\\Users\Joe\data.txt", "C:\\Users\Joe\hello.txt")

This will rename the file "data.txt" to "hello.txt".

We can delete a folder and all of its contents using the shutil.rmtree(path) function.

Knowledge Check

How do we find our current working directory with the pathlib module? What is it in the os module?
What is the difference between the os and the pathlib modules?
How do we rename a file in the shutil module?

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