Searching Files by Content/Extension

diagram searching by name is cheap; searching by content is not mermaid

  flowchart TD
  A["os.walk / rglob"] --> B["prune directories you never want"]
  B --> C{"does the name match?"}
  C -->|no| D["skip -- no file was opened"]
  C -->|yes| E{"searching content too?"}
  E -->|no| F["report it"]
  E -->|yes| G["open it"]
  G --> H{"is it text?"}
  H -->|no| I["UnicodeDecodeError -- catch it, or open in binary"]
  H -->|yes| J["scan line by line, not read()"]
  J --> K["report the path and line number"]

Filtering on the filename only needs the directory listing the walk already gave you. Looking inside means opening every candidate, which is where the cost is -- so narrow by extension and size first, read in chunks rather than whole, and be ready for files that are not text at all.

Find files by extension

find_by_extension.py

from pathlib import Path
 
root = Path(".")
for p in root.rglob("*.md"):
    print(p)

Search file contents

This example searches for a word in .py files.

search_content.py

from pathlib import Path
 
 
def search_word(root: Path, word: str):
    for p in root.rglob("*.py"):
        try:
            text = p.read_text(encoding="utf-8")
        except UnicodeDecodeError:
            continue
 
        if word in text:
            print("found in", p)
 
 
search_word(Path("."), "asyncio")

Tips

skip binary files
limit walking large folders
consider ripgrep for huge repos

🧪 Try It Yourself

Exercise 1 – List Files with os.listdir

Exercise 2 – Join Paths with os.path.join

Exercise 3 – Write and Read a File

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