Creating a Directory and its Parent Directories in Python

Introduction

In Python, we often need to interact with the file system, whether it's reading files, writing to them, or creating directories. This Byte will focus on how to create directories in Python, and more specifically, how to create a directory and any missing parent directories. We'll be exploring the os.mkdir and os.makedirs functions for this purpose.

Why do we need to create the parent directories?

When working with file systems, which is common for system utilities or tools, you'll likely need to create a directory at a certain path. If the parent directories of that path don't exist, you'll encounter an error.

To avoid this, you'll need to create all necessary parent directories since the OS/filesystem doesn't handle this for you. By ensuring all the necessary parent directories exist before creating the target directory, you can avoid these errors and have a more reliable codebase.

Creating a Directory Using os.mkdir

The os.mkdir function in Python is used to create a directory. This function takes the path of the new directory as an argument. Here's a simple example:

import os

os.mkdir('my_dir')

This will create a new directory named my_dir in the current working directory. However, os.mkdir has a limitation - it can only create the final directory in the specified path, and assumes that the parent directories already exist. If they don't, you'll get a FileNotFoundError.

import os

os.mkdir('parent_dir/my_dir')

If parent_dir doesn't exist, this code will raise a FileNotFoundError.

Note: The os.mkdir function will also raise a FileExistsError if the directory you're trying to create already exists. It's always a good practice to check if a directory exists before trying to create it. To do this, you can pass the exist_ok=True argument, like this: os.makedirs(path, exist_ok=True). This will make the function do nothing if the directory already exists.

One way to work around the limitation of os.mkdir is to manually check and create each parent directory leading up to the target directory. The easiest way to approach this problem is to split our path by the slashes and check each one. Here's an example of how you can do that:

import os

path = 'parent_dir/sub_dir/my_dir'

# Split the path into parts
parts = path.split('/')

# Start with an empty directory path
dir_path = ''

# Iterate through the parts, creating each directory if it doesn't exist
for part in parts:
    dir_path = os.path.join(dir_path, part)
    if not os.path.exists(dir_path):
        os.mkdir(dir_path)

This code will create parent_dir, sub_dir, and my_dir if they don't already exist, ensuring that the parent directories are created before the target directory.

However, there's a more concise way to achieve the same goal by using the os.makedirs function, which we'll see in the next section.

Creating Parent Directories Using os.makedirs

To overcome the limitation of os.mkdir, Python provides another function - os.makedirs. This function creates all the intermediate level directories needed to create the final directory. Here's how you can use it:

import os

os.makedirs('parent_dir/my_dir')

In this case, even if parent_dir doesn't exist, os.makedirs will create it along with my_dir. If parent_dir already exists, os.makedirs will simply create my_dir within it.

Note: Like os.mkdir, os.makedirs will also raise a FileExistsError if the final directory you're trying to create already exists. However, it won't raise an error if the intermediate directories already exist.

Using pathlib to Create Directories

The pathlib module in Python 3.4 and above provides an object-oriented approach to handle filesystem paths. It's more intuitive and easier to read than using os.mkdir or os.makedirs. To create a new directory with pathlib, you can use the Path.mkdir() method.

Here is an example:

from pathlib import Path

# Define the path
path = Path('/path/to/directory')

# Create the directory
path.mkdir(parents=True, exist_ok=True)

In this code, the parents=True argument tells Python to create any necessary parent directories, and exist_ok=True allows the operation to proceed without raising an exception if the directory already exists.

Handling Exceptions when Creating Directories

When working with filesystems, it's always a good idea to handle exceptions. This could be due to permissions, the directory already existing, or a number of other unforeseen issues. Here's one way to handle exceptions when creating your directories:

from pathlib import Path

# Define the path
path = Path('/path/to/directory')

try:
    # Create the directory
    path.mkdir(parents=True, exist_ok=False)
except FileExistsError:
    print("Directory already exists.")
except PermissionError:
    print("You don't have permissions to create this directory.")
except Exception as e:
    print(f"An error occurred: {e}")

In this code, we've set exist_ok=False to raise a FileExistsError if the directory already exists. We then catch this exception, along with PermissionError and any other exceptions, and print a relevant message. This gives us more fine-grained control over what we do when certain situations arise, although it's less concise and hurts readability.

When to use os or pathlib for Creating Directories

Choosing between os and pathlib for creating directories largely depends on your specific use case and personal preference.

The os module has been around for a while and is widely used for interacting with the operating system. It's a good choice if you're working with older versions of Python or if you need to use other os functions in your code.

On the other hand, pathlib is a newer module that provides a more intuitive, object-oriented approach to handling filesystem paths. It's a good choice if you're using Python 3.4 or above and prefer a more modern, readable syntax.

Luckily, both os and pathlib are part of the standard Python library, so you won't need to install any additional packages to use them.

Conclusion

In this Byte, we've explored how to create directories and handle exceptions using the os and pathlib modules in Python. Remember that choosing between these two options depends on your specific needs and personal preferences. Always be sure to handle exceptions when working with filesystems to make your code more robust and reliable. This is important as it's easy to make mistakes when working with filesystems and end up with an error.