Recursive File Searching in Python

Often, you’ll need to locate files within a directory structure, not just in the immediate directory, but also within any nested subdirectories. This is known as recursive file searching. Python provides several ways to accomplish this, ranging from built-in modules to more modern approaches using the pathlib module. This tutorial will cover the most common and effective techniques.

Understanding the Problem

Imagine you have a directory structure like this:

src/
├── main.c
├── dir/
│   └── file1.c
└── another-dir/
    ├── file2.c
    └── nested/
        └── files/
            └── file3.c

The goal is to find all files with the .c extension within the src directory, including those deeply nested within subdirectories. A simple os.listdir() won’t suffice, as it only lists the contents of the immediate directory.

1. Using `os.walk()`

The os.walk() function is a powerful tool for traversing directory trees. It yields a 3-tuple for each directory it visits: the root directory, a list of subdirectory names, and a list of filenames.

Here’s how you can use it to find files recursively:

import os

def find_files(directory, pattern):
    """
    Recursively searches for files matching a given pattern within a directory.

    Args:
        directory: The root directory to start the search from.
        pattern:  A filename pattern to match (e.g., "*.c").

    Returns:
        A list of full paths to the matching files.
    """
    matches = []
    for root, _, files in os.walk(directory):
        for filename in files:
            if filename.endswith(pattern[1:]):  #Check file extention
                matches.append(os.path.join(root, filename))
    return matches

# Example usage:
directory_to_search = "src"
file_pattern = "*.c"
found_files = find_files(directory_to_search, file_pattern)

for file in found_files:
    print(file)

This code iterates through each directory and its files. The endswith() method efficiently checks if a filename matches the specified pattern. This method is particularly useful for older Python versions.

2. Using `glob.glob()` with Recursive Support (Python 3.5+)

Python 3.5 introduced recursive globbing using the ** wildcard in the glob module. This provides a concise way to search for files recursively.

import glob

directory_to_search = "src"
file_pattern = "**/*.c" # The ** means search recursively
found_files = glob.glob(directory_to_search + "/" + file_pattern, recursive=True)

for file in found_files:
    print(file)

The recursive=True argument tells glob() to search recursively through subdirectories. This is generally the simplest and most readable approach for modern Python versions. Remember to include the directory prefix and a forward slash for the pattern to work correctly.

3. Using `pathlib.Path.rglob()` (Python 3.5+)

The pathlib module provides an object-oriented way to interact with files and directories. Its rglob() method recursively glob a directory.

from pathlib import Path

directory_to_search = Path("src")
file_pattern = "*.c"
found_files = [str(file) for file in directory_to_search.rglob(file_pattern)] #convert Path objects to strings

for file in found_files:
    print(file)

This approach is considered more Pythonic and object-oriented. rglob() returns Path objects, which you may need to convert to strings using str() if you require string paths.

Choosing the Right Method

For Python versions older than 3.5, os.walk() is the most reliable option.
For Python 3.5 and later, glob.glob(recursive=True) and pathlib.Path.rglob() offer more concise and readable solutions. pathlib is often preferred for its object-oriented nature.

Consider the specific requirements of your project and choose the method that best balances readability, performance, and compatibility.