File Operations & JSON in Python
From the Python cheat sheet · File I/O · verified Jul 2026
File Operations & JSON
Read, write, and append files. Parse and write JSON data.
python
# Read a file
with open("data.txt") as f:
content = f.read()
# Write a file
with open("output.txt", "w") as f:
f.write("Hello!")
# JSON
import json
data = json.loads('{"name": "Alice"}')
json_str = json.dumps(data, indent=2)💡 Always use "with open(...)" — it automatically closes the file
⚡ json.load/dump work with files; json.loads/dumps work with strings
📌 Use pathlib.Path for cross-platform path handling — it's the modern approach
🟢 Read large files line-by-line with "for line in f:" to save memory
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