Working with JSON files

• JSON is the standard format for data exchange in web services and cloud APIs.
• Python’s built-in json module provides functions to convert between JSON text and Python objects.
• Key operations: parsing JSON from strings/files and serializing Python objects to JSON strings/files.

JSON Syntax and Python Mapping

• JSON objects ({}) map to Python dict.
• JSON arrays ([]) map to Python list.
• JSON strings map to Python str, numbers to int or float.
• true/false → True/False; null → None.
• Keys in JSON objects must be double-quoted strings; no trailing commas.

Deserializing JSON

• Use json.loads() to parse JSON strings into Python objects.
• Raises json.JSONDecodeError on invalid JSON.
• Common in DevOps for handling API response bodies.

import json

api_response_str = '{"status": "active", "instance_id": "i-12345", "cores": 4, "tags": ["web", "prod"]}'

try:
    data = json.loads(api_response_str)
    print(f"Parsed data type: {type(data)}")
    print(f"Instance ID: {data.get("instance_id", None)}")
    print(f"Tags: {data.get("tags", None)}")
except json.JSONDecodeError as e:
    print(f"Failed to parse JSON: {e}")

Parsing JSON Files

• Use json.load() to read JSON from an open file object.
• Always open files with encoding='utf-8' when dealing with JSON.
• Wrap file operations in with to ensure proper closure.

import json
from pathlib import Path

config_path = Path("service_config.json")

with config_path.open("r", encoding="utf-8") as file:
    config_data = json.load(file)

for config in config_data:
    service_name = config.get("service", None)

    if service_name:
        print(f"Service: {service_name}")
        print(f"Enabled: {config.get("enabled", False)}")
        print('-' * 20)

Example of service_config.json

[
  {
    "service": "database",
    "port": 5432,
    "connection_pool": 10,
    "enabled": true
  },
  {
    "service": "cache",
    "port": 6379,
    "connection_pool": 5
  },
  {
    "service": "api",
    "port": 8080,
    "connection_pool": 3,
    "enabled": true
  },
  {
    "port": 5000,
    "connection_pool": 3,
    "enabled": true
  }
]

Serializing Python objects to JSON Strings

• Use json.dumps() to convert Python objects to JSON strings.
• indent makes output human-readable; sort_keys=True orders keys alphabetically.

import json

python_data = {
    "deployment": "frontend-v2",
    "replicas": 3,
    "ports": [80, 443],
    "health_check": True,
    "logs_enabled": None
}

print(f"Simple JSON:\n{json.dumps(python_data)}")
print("\n")
print(f"Pretty JSON:\n{json.dumps(python_data, indent=2, sort_keys=True)}")

Serializing Python objects to JSON Files

• Use json.dump() to write Python objects directly to files.
• Pass the file handle and optional indent for formatting.

import json
from pathlib import Path

output = {
    "status": "complete",
    "items_processed": 1492,
    "errors": []
}
output_path = Path("run_summary.json")

with output_path.open("w", encoding="utf-8") as file:
    json.dump(output, file, indent=2)