Read and Write JSON Files Idiomatically

import json
import tempfile
import os

with tempfile.TemporaryDirectory() as tmp:
    path = os.path.join(tmp, 'config.json')

    config = {
        'name': 'CodeSnatch',
        'version': 3,
        'features': ['lessons', 'practice'],
        'owner': {'team': 'platform', 'on_call': 'ana'},
    }

    # Always pair `with` + explicit encoding. UTF-8 is the JSON default.
    with open(path, 'w', encoding='utf-8') as f:
        json.dump(config, f, indent=2, ensure_ascii=False)

    with open(path, 'r', encoding='utf-8') as f:
        loaded = json.load(f)

    print(loaded['features'])         # ['lessons', 'practice']
    print(loaded == config)           # True

import json
import tempfile
import os

user = {
    'name': 'José Müller',
    'note': 'café, naïve, façade',
    'emoji': '\U0001F600',
}

with tempfile.TemporaryDirectory() as tmp:
    path = os.path.join(tmp, 'user.json')

    # Wrong defaults: ensure_ascii=True turns every non-ASCII char into \uXXXX.
    bad = json.dumps(user, indent=2)
    print('default (ASCII-escaped):')
    print(bad)

    # Right defaults for human-readable files: indent + UTF-8 raw text.
    good = json.dumps(user, indent=2, ensure_ascii=False, sort_keys=True)
    print()
    print('readable:')
    print(good)

    with open(path, 'w', encoding='utf-8') as f:
        f.write(good)

    print('size on disk:', os.path.getsize(path), 'bytes')

import json
import os
import tempfile

def atomic_write_json(path, data):
    """Write JSON to `path` atomically: a crash mid-write cannot corrupt it."""
    directory = os.path.dirname(os.path.abspath(path))
    os.makedirs(directory, exist_ok=True)
    # NamedTemporaryFile in the same directory so os.replace stays on one filesystem.
    fd, tmp_path = tempfile.mkstemp(prefix='.tmp-', dir=directory, suffix='.json')
    try:
        with os.fdopen(fd, 'w', encoding='utf-8') as f:
            json.dump(data, f, indent=2, ensure_ascii=False, sort_keys=True)
            f.flush()
            os.fsync(f.fileno())
        os.replace(tmp_path, path)  # atomic on POSIX and Windows
    except Exception:
        # Cleanup the temp file if anything went wrong.
        try:
            os.unlink(tmp_path)
        except FileNotFoundError:
            pass
        raise

with tempfile.TemporaryDirectory() as tmp:
    target = os.path.join(tmp, 'config.json')
    atomic_write_json(target, {'version': 1, 'name': 'demo'})
    with open(target, encoding='utf-8') as f:
        print(f.read())
    print('done, file size:', os.path.getsize(target))