How to Save and Load JSON Files in Python

Create a simple data helper to save Python dictionaries as pretty-printed JSON files and load them back reliably using pathlib and the stdlib json module.

Easy Python 3.9+ Aug 9, 2026 Modern tooling 11 views 0 copies

json pathlib file-io data-helper stdlib

Python code

24 lines

Python 3.9+

import json
from pathlib import Path
from typing import Any


def save_json(data: Any, filename: str) -> None:
    """Save data as pretty-printed JSON to the current directory."""
    path = Path(filename)
    with path.open("w", encoding="utf-8") as f:
        json.dump(data, f, indent=2, ensure_ascii=False)


def load_json(filename: str) -> Any:
    """Load and return data from a JSON file."""
    path = Path(filename)
    with path.open("r", encoding="utf-8") as f:
        return json.load(f)


if __name__ == "__main__":
    sample = {"name": "Mira", "skills": ["Python", "JSON"], "level": 3}
    save_json(sample, "sample_data.json")
    loaded = load_json("sample_data.json")
    print(loaded)

Output

stdout

{'name': 'Mira', 'skills': ['Python', 'JSON'], 'level': 3}

How it works

The save_json function uses pathlib.Path to open a file for writing and json.dump with indent=2 and ensure_ascii=False to produce readable JSON that preserves non-ASCII characters. The load_json function opens the file for reading and json.load parses the content back into a Python dictionary. Running the script as the main module creates sample_data.json in the current directory, then reads it back and prints the dictionary with standard Python syntax. This pattern cleanly separates file I/O from business logic, making it reusable across projects.

Common mistakes

Calling `json.dumps` instead of `json.dump` when writing directly to a file, then forgetting to close it manually.
Hardcoding file paths without `pathlib`, which breaks on different operating systems.
Not using `ensure_ascii=False`, so non-English characters get escaped to \u sequences in the output file.

Variations

Use `Path.read_text()` and `Path.write_text()` with `json.loads` and `json.dumps` for even shorter file I/O.
Add a `pretty=True` parameter to toggle indentation, or support append mode for log-style JSON lines.

Real-world use cases

Persisting user preferences or app settings to a configuration file that must be human-readable.
Caching API responses locally so subsequent runs don't hit the network again.
Exporting processed data to a JSON file for sharing with other tools or non-Python systems.

How to Save and Load JSON Files in Python

Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

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