Simplejson

3.20.2 · active · verified Sat Mar 28

Simplejson is a fast, extensible, and standards-compliant JSON encoder/decoder for Python. It's often used as a drop-in replacement for Python's built-in `json` module, offering a C extension for improved performance and additional features. The library is actively maintained, with the current stable version being 3.20.2, and releases occur several times a year.

Warnings

breaking In versions 3.19.1 and later, security hardening measures changed default behavior to be more strict, consuming and producing only compliant JSON by default. If your application previously relied on non-compliant JSON features being tolerated (e.g., non-string keys if `use_decimal=True`), you might need to adjust your data or explicitly re-enable older, less strict behaviors using specific flags.
Fix: Review the `simplejson.JSONDecoder` and `simplejson.JSONEncoder` options for flags that can re-enable specific non-compliant behaviors if absolutely necessary, but it's recommended to update your JSON data to be strictly compliant.
gotcha simplejson disables C speedups on specific Python runtimes (e.g., PyPy, GraalPy) where they are not compatible or provide no benefit. If you are using these runtimes, expect equivalent performance to the pure-Python implementation.
Fix: No fix needed; this is an expected behavior for compatibility and stability on specific runtimes.
gotcha Versions 3.20.0 and 3.20.1 changed key memoization behavior to ensure keys are coerced to strings before memoization. While unlikely to cause direct breaks, if you had highly specific reliance on the internal memoization of non-string keys (e.g., custom objects used as keys that were not string-coerced until later stages), this might subtly alter behavior or performance profiles.
Fix: Ensure that keys in objects intended for JSON serialization are inherently string-compatible or are handled explicitly. Most common use cases should not be affected.

Install

pip install simplejson Install stable version

Imports

simplejson
```
import simplejson
```
While often used as a drop-in replacement, it is its own module and should be imported as 'simplejson'.
loads
```
simplejson.loads
```
'load' is for file-like objects, 'loads' is for strings.
dumps
```
simplejson.dumps
```
'dump' is for file-like objects, 'dumps' is for strings.

Quickstart

This quickstart demonstrates encoding a Python dictionary into a formatted JSON string using `simplejson.dumps` and then decoding it back into a Python object using `simplejson.loads`.

import simplejson

data = {'name': 'Alice', 'age': 30, 'is_student': False, 'courses': ['Math', 'Science']}

# Encode Python object to JSON string
json_string = simplejson.dumps(data, indent=4)
print('Encoded JSON:')
print(json_string)

# Decode JSON string to Python object
decoded_data = simplejson.loads(json_string)
print('\nDecoded Data:')
print(decoded_data)
print(f"Accessing a value: {decoded_data['name']}")

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