What are the differences between json and simplejson Python modules?

Both json and simplejson are Python modules for working with JSON data, but they have key differences in availability, performance, and update frequency.

What is json?

The json module is part of Python's standard library since Python 2.6. It provides basic JSON encoding and decoding functionality ?

import json

data = {"name": "Alice", "age": 30, "city": "New York"}
json_string = json.dumps(data)
print(json_string)

# Parse JSON back to Python object
parsed_data = json.loads(json_string)
print(parsed_data)

{"name": "Alice", "age": 30, "city": "New York"}
{'name': 'Alice', 'age': 30, 'city': 'New York'}

What is simplejson?

The simplejson module is an external library that can be installed via pip. It's the original JSON library that was later incorporated into Python's standard library ?

# First install: pip install simplejson
import simplejson as json

data = {"product": "laptop", "price": 999.99, "available": True}
json_string = json.dumps(data)
print(json_string)

{"product": "laptop", "price": 999.99, "available": true}

Key Differences

Best Practice: Fallback Pattern

A common approach is to try importing simplejson first, then fall back to the standard json module ?

try:
    import simplejson as json
except ImportError:
    import json

# Now use json regardless of which module was imported
data = {"message": "Hello World", "status": "success"}
result = json.dumps(data, indent=2)
print(result)

{
  "message": "Hello World",
  "status": "success"
}

When to Use Each

Use json when:

• Working with Python 2.6+ or Python 3
• You want to avoid external dependencies
• Standard performance is sufficient

Use simplejson when:

• Supporting older Python versions (2.4−2.5)
• You need the latest optimizations and features
• Performance is critical

Conclusion

The json module is simplejson integrated into Python's standard library. Use the fallback pattern to get the best of both worlds − simplejson's performance when available, with json as a reliable fallback.