How can I efficiently search for and list files within subfolders using Python?

Recursive Subfolder Search and File Listing

It is common to encounter scenarios where you need to traverse through multiple subfolders and extract specific files based on their file extension. One approach to tackle this is by leveraging Python's built-in os.walk function, which enables recursive exploration of directories and their contents.

However, as encountered in this question, the problematic behavior arises when attempting to concatenate the files' paths. The subFolder variable returned by os.walk represents a list of subfolders rather than the specific folder where each file resides.

To remedy this issue, the correct approach is to utilize the dirpath (or root in the given code), which represents the current directory for the iteration. The dirpath value should be concatenated with the file name to construct the complete file path.

Furthermore, it is important to consider additional factors such as pruning certain folders from the recursion process, which can be achieved by examining the dn (dirname) list. To avoid relying on string manipulation for file extension checks, you can leverage the os.path.splitext function.

Here is an optimized version of the code that incorporates these enhancements:

<code class="python">import os
result = [
    os.path.join(dp, f)
    for dp, dn, filenames in os.walk(PATH)
    for f in filenames
    if os.path.splitext(f)[1] == ".txt"
]</code>

As an alternative, glob is another powerful tool that can be employed to select files based on their extensions. Here's an example using glob:

<code class="python">import os
from glob import glob

result = [
    y
    for x in os.walk(PATH)
    for y in glob(os.path.join(x[0], "*.txt"))
]</code>

For Python 3.4 , Pathlib provides an intuitive approach for this task:

<code class="python">from pathlib import Path

result = list(Path(".").rglob("*.[tT][xX][tT]"))</code>

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