How to Find Files by Extension in Python

This code walks a directory tree with pathlib, collects all file paths, and counts them by extension to summarize a project's contents.

Easy Python 3.9+ Aug 9, 2026 Files & data 12 views 0 copies

pathlib file-system recursion extension-counting file-listing

Python code

24 lines

Python 3.9+

from pathlib import Path

def get_project_files(base_path="."):
    """Return a sorted list of all file paths under base_path."""
    base = Path(base_path)
    files = [p for p in base.rglob("*") if p.is_file()]
    return sorted(files)

def count_by_extension(files):
    """Return a dict mapping extension (lowercase) to file count."""
    counts = {}
    for f in files:
        ext = f.suffix.lower() or "no_extension"
        counts[ext] = counts.get(ext, 0) + 1
    return counts

if __name__ == "__main__":
    files = get_project_files(".")
    print(f"Total files: {len(files)}")
    for ext, count in sorted(count_by_extension(files).items()):
        print(f"{ext}: {count}")
    print("\nFirst 5 files:")
    for f in files[:5]:
        print(f)

Output

stdout

Total files: 12
.md: 2
.py: 5
.txt: 3
no_extension: 2

First 5 files:
README.md
setup.py
src/main.py
src/utils.py
tests/test_app.py

How it works

The Path.rglob method recursively matches all files and directories, with is_file() filtering out folders. Using a list comprehension keeps the code concise and readable. The suffix property returns the file extension including the dot, and lowercasing it ensures consistent grouping. The get method with a default of 0 avoids KeyError when incrementing counts. Sorting the final list makes output deterministic, which is helpful for testing and reproducibility.

Common mistakes

Forgetting to call `.is_file()` so directories are included in the results
Not lowercasing extensions, causing `.PY` and `.py` to count separately
Assuming the count dict preserves insertion order without sorting when printing

Variations

Use `os.walk` from the standard library instead of pathlib for older Python versions
Use `collections.Counter` to replace the manual counting loop

Real-world use cases

Summarizing a codebase before a refactor to understand file type distribution.
Building a cleanup script that identifies orphaned or duplicate files by extension.
Generating a manifest of project files for packaging or deployment artifacts.

How to Find Files by Extension in Python

Python code

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How it works

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