pathlib & Modern File Handling

Also Known As

TL;DR

Explanation

pathlib (Python 3.4+) represents paths as Path objects with methods: / operator joins paths, .read_text() / .write_text() / .read_bytes(), .exists() / .is_file() / .is_dir(), .glob() / .rglob() for pattern matching, .stem / .suffix / .parent / .name attributes, .mkdir(parents=True, exist_ok=True). Avoids the fragile string concatenation of os.path.join(). Works correctly on Windows (backslash) and Unix (forward slash). Use Path objects from the start — do not mix Path and string manipulation.

Common Misconception

Why It Matters

Common Mistakes

• Mixing string concatenation with Path objects — always use / operator or Path() constructor.
• Not using exist_ok=True in mkdir — raises if directory exists.
• glob() not being recursive — use rglob('**/*.py') or rglob with a pattern for recursive matching.
• Converting Path to string with str() when passing to legacy APIs — unnecessary in modern Python.

Code Examples

import os

# String-based path manipulation — fragile:
base = '/var/www/app'
config_path = base + '/config' + '/settings.json'  # Wrong on Windows
if os.path.exists(config_path):
    with open(config_path) as f:
        data = f.read()
os.makedirs(os.path.join(base, 'logs'), exist_ok=True)

from pathlib import Path

base = Path('/var/www/app')
config_path = base / 'config' / 'settings.json'  # / operator, cross-platform

if config_path.exists():
    data = config_path.read_text(encoding='utf-8')  # No with-open needed

(base / 'logs').mkdir(parents=True, exist_ok=True)

# Find all Python files recursively:
for py_file in base.rglob('*.py'):
    print(py_file.stem, py_file.suffix)

References

• ↗ https://docs.python.org/3/library/pathlib.html

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