Safe atomic file writes for JSON and YAML in Python 3

atomic_write.py

import json
import os
import shutil
import stat
import tempfile
import yaml

def copy_with_metadata(source, target):
    """Copy file with all its permissions and metadata.
    
    Lifted from https://stackoverflow.com/a/43761127/2860309
    :param source: source file name
    :param target: target file name
    """
    # copy content, stat-info (mode too), timestamps...
    shutil.copy2(source, target)
    # copy owner and group
    st = os.stat(source)
    os.chown(target, st[stat.ST_UID], st[stat.ST_GID])

def atomic_write(file_contents, target_file_path, mode="w"):
    """Write to a temporary file and rename it to avoid file corruption.

    Attribution: @therightstuff, @deichrenner, @hrudham
    :param file_contents: contents to be written to file
    :param target_file_path: the file to be created or replaced
    :param mode: the file mode defaults to "w", only "w" and "a" are supported
    """
    # Use the same directory as the destination file so that moving it across
    # file systems does not pose a problem.
    temp_file = tempfile.NamedTemporaryFile(
        delete=False,
        dir=os.path.dirname(target_file_path))
    try:
        # preserve file metadata if it already exists
        if os.path.exists(target_file_path):
            copy_with_metadata(target_file_path, temp_file.name)
        with open(temp_file.name, mode) as f:
            f.write(file_contents)
            f.flush()
            os.fsync(f.fileno())

        os.replace(temp_file.name, target_file_path)
    finally:
        if os.path.exists(temp_file.name):
            try:
                os.unlink(temp_file.name)
            except:
                pass

# example lifted from https://www.debugcn.com/en/article/37223857.html
data = [{'item': 'Food_eat', 'Food': {'foodNo': 42536216,'type': 'fruit','moreInfo': ['organic']}}]

yaml_content = yaml.safe_dump(data, default_flow_style=False)

atomic_write(yaml_content, "./sample.yaml")

json_content = json.dumps(data, indent=4)

atomic_write(json_content, "./sample.json")

output.json

[
    {
        "item": "Food_eat",
        "Food": {
            "foodNo": 42536216,
            "type": "fruit",
            "moreInfo": [
                "organic"
            ]
        }
    }
]

output.yaml

- Food:
    foodNo: 42536216
    moreInfo:
    - organic
    type: fruit
  item: Food_eat