json.dump and json.load (File I/O)¶

dump() writes JSON to a file, while load() reads JSON from a file.

dump - Write JSON to File¶

Write JSON data directly to a file.

```python import json import tempfile import os

data = { "users": [ {"id": 1, "name": "Alice"}, {"id": 2, "name": "Bob"} ] }

Write to file¶

with tempfile.NamedTemporaryFile(mode='w', suffix='.json', delete=False) as f: json.dump(data, f) temp_path = f.name

Verify¶

with open(temp_path) as f: print(f.read())

os.unlink(temp_path) ```

{"users": [{"id": 1, "name": "Alice"}, {"id": 2, "name": "Bob"}]}

load - Read JSON from File¶

Read JSON data directly from a file.

```python import json import tempfile import os

Create temporary JSON file¶

data = {"config": {"host": "localhost", "port": 8080}} with tempfile.NamedTemporaryFile(mode='w', suffix='.json', delete=False) as f: json.dump(data, f) temp_path = f.name

Load from file¶

with open(temp_path) as f: loaded = json.load(f) print(loaded) print(f"Host: {loaded['config']['host']}")

os.unlink(temp_path) ```

{'config': {'host': 'localhost', 'port': 8080}} Host: localhost

Exercises¶

Exercise 1. Write a function save_and_load that takes a Python dictionary, writes it to a temporary JSON file with pretty formatting (indent=2), reads it back, and returns the loaded dictionary. Verify the round-trip produces an equal dictionary.

with open(path) as f:
    loaded = json.load(f)

os.unlink(path)
return loaded

Exercise 2. Write a function merge_json_files that takes a list of JSON file paths, loads each one, and merges them into a single dictionary (later files override earlier ones for duplicate keys). Return the merged dictionary.

Exercise 3. Write a function update_json_field that takes a file path, a key, and a new value. It should load the JSON file, update the specified key, and write the file back. If the file does not exist, create it with just that key-value pair.

data[key] = value

with open(file_path, 'w') as f:
    json.dump(data, f, indent=2)