Skip to main content

Build complex rules, serialize them as JSON, and execute them in Python

Project description

This parser accepts JsonLogic rules and executes them in Python.

This is a Python porting of the excellent GitHub project by jwadhams for JavaScript: json-logic-js.

All credit goes to him, this is simply an implementation of the same logic in Python (small differences below).

The JsonLogic format is designed to allow you to share rules (logic) between front-end and back-end code (regardless of language difference), even to store logic along with a record in a database. JsonLogic is documented extensively at JsonLogic.com, including examples of every supported operation and a place to try out rules in your browser.

The same format can also be executed in PHP by the library json-logic-php

Examples

Simple

from json_logic import jsonLogic
jsonLogic( { "==" : [1, 1] } )
# True

This is a simple test, equivalent to 1 == 1. A few things about the format:

  1. The operator is always in the “key” position. There is only one key per JsonLogic rule.

  2. The values are typically an array.

  3. Each value can be a string, number, boolean, array (non-associative), or null

Compound

Here we’re beginning to nest rules.

jsonLogic(
  {"and" : [
    { ">" : [3,1] },
    { "<" : [1,3] }
  ] }
)
# True

In an infix language (like Python) this could be written as:

( (3 > 1) and (1 < 3) )

Data-Driven

Obviously these rules aren’t very interesting if they can only take static literal data. Typically jsonLogic will be called with a rule object and a data object. You can use the var operator to get attributes of the data object:

jsonLogic(
  { "var" : ["a"] }, # Rule
  { a : 1, b : 2 }   # Data
)
# 1

If you like, we support syntactic sugar on unary operators to skip the array around values:

jsonLogic(
  { "var" : "a" },
  { a : 1, b : 2 }
)
# 1

You can also use the var operator to access an array by numeric index:

jsonLogic(
  {"var" : 1 },
  [ "apple", "banana", "carrot" ]
)
# "banana"

Here’s a complex rule that mixes literals and data. The pie isn’t ready to eat unless it’s cooler than 110 degrees, and filled with apples.

rules = { "and" : [
  {"<" : [ { "var" : "temp" }, 110 ]},
  {"==" : [ { "var" : "pie.filling" }, "apple" ] }
] }

data = { "temp" : 100, "pie" : { "filling" : "apple" } }

jsonLogic(rules, data)
# True

Always and Never

Sometimes the rule you want to process is “Always” or “Never.” If the first parameter passed to jsonLogic is a non-object, non-associative-array, it is returned immediately.

#Always
jsonLogic(True, data_will_be_ignored);
# True

#Never
jsonLogic(False, i_wasnt_even_supposed_to_be_here);
# False

Installation

The best way to install this library is via PIP:

pip install json-logic

If that doesn’t suit you, and you want to manage updates yourself, the entire library is self-contained in json_logic.py and you can download it straight into your project as you see fit.

curl -O https://raw.githubusercontent.com/nadirizr/json-logic-py/master/json_logic.py

Project details


Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

json_logic-0.7.0a0.tar.gz (6.3 kB view details)

Uploaded Source

Built Distribution

json_logic-0.7.0a0-py2.py3-none-any.whl (7.6 kB view details)

Uploaded Python 2Python 3

File details

Details for the file json_logic-0.7.0a0.tar.gz.

File metadata

  • Download URL: json_logic-0.7.0a0.tar.gz
  • Upload date:
  • Size: 6.3 kB
  • Tags: Source
  • Uploaded using Trusted Publishing? No

File hashes

Hashes for json_logic-0.7.0a0.tar.gz
Algorithm Hash digest
SHA256 84580b974bcfec7b00d63745f19ca363939fc2b93c579f578d41d7d10c12fe0c
MD5 689d04e0a3a388c0ef63408b8c925cd4
BLAKE2b-256 7d055b516986c0706b7ae5f4b2155b1c32979479b378b55c0dd9bcc48e70fc5d

See more details on using hashes here.

File details

Details for the file json_logic-0.7.0a0-py2.py3-none-any.whl.

File metadata

File hashes

Hashes for json_logic-0.7.0a0-py2.py3-none-any.whl
Algorithm Hash digest
SHA256 a7af2e3673212279b4c7b63d0b0ead5f6b3d89cef8970bdbf60595d3bc9dd819
MD5 86ff82eb68b7e04f7cf57144013e0d8e
BLAKE2b-256 47cc65de2481a8b7fae1582c564527d47ecae82f9c9e7ba60ad570b012f22634

See more details on using hashes here.

Supported by

AWS Cloud computing and Security Sponsor Datadog Monitoring Fastly CDN Google Download Analytics Pingdom Monitoring Sentry Error logging StatusPage Status page