Python File I/O

Skip `os.path` and string concatenation. `pathlib.Path` handles cross-platform paths, reads, writes, and checks existence in one object.

from pathlib import Path
import json

data_dir = Path("data")
data_dir.mkdir(exist_ok=True)

record = {"user": "Ada", "score": 91}

out = data_dir / "record.json"
out.write_text(json.dumps(record, indent=2), encoding="utf-8")

loaded = json.loads(out.read_text(encoding="utf-8"))
print(loaded["score"])  # 91

Line-by-line for big files

with open("big.log", encoding="utf-8") as f:
    errors = [line for line in f if "ERROR" in line]

print(f"found {len(errors)} errors")

Understanding "Python File I/O" in practice: AI can help you write, fix, and understand code faster than ever — even if you're just learning. Reading and writing files is where real scripts start. Learn the with-statement, path handling, and JSON round-trips — and knowing how to apply this gives you a concrete advantage.

• Apply pathlib in your ai-coding workflow to get better results
• Apply with in your ai-coding workflow to get better results
• Apply json in your ai-coding workflow to get better results
• Apply encoding in your ai-coding workflow to get better results

1. 1Use AI to generate unit tests for an existing function
2. 2Ask AI to refactor a messy function and explain the changes
3. 3Have AI suggest a code review for a recent pull request

The big idea: pathlib for paths, context managers for safety, explicit utf-8 everywhere. That covers nine out of ten I/O tasks.