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A JSONPath implementation for Python

Project description

JSONPyth

Build Status

Another JSONPath implementation for Python.

Supports:

  • Root $ and current @ node
  • Child operator . or [ ... ]
  • Property access (including single quote ' and double " quote delimited names)
  • Recursive descent ..
  • Wildcard *
  • Sets of names/indices [a,b,c]
  • Array slice [start:end:step] (including negative values)
  • Python script expression ( ... ) and filter expression ?( ... ) using $ and @

Requirements

Requires Python 3.5+ and depends on the PyParsing package.

Installation

JSONPyth can be git-cloned directly from Github and installed along with its dependencies using pip:

$ pip install git+https://github.com/Frimkron/JSONPyth#egg=JSONPyth

Or the source can be downloaded manually and then installed by running the setup.py script:

$ python setup.py install

Usage

First parse some JSON data into a Python structure, for example using the json package from the standard library:

import json

# parse some JSON from a string
data = json.loads("""
    {
        "cakes": [
            { "name": "red velvet", "rating": 4.5 },
            { "name": "battenberg" },
            { "name": "jaffa cakes", "rating": 5.0 }
        ],
        "biscuits": [
            { "name": "bourbon", "rating": 5.0 },
            { "name": "custard cream", "rating": 3.5 },
            { "name": "pink wafer", "rating": null },
            { "name": "nice" }
        ]
    }
""")

Then the data can be queried with a JSONPath expression:

from jsonpyth import jsonpath

result = jsonpath(data, '$.biscuits[*].rating')

for r in result:
    print(r)
    

The example above would print the following output:

5
3.5
None

Returning Paths

By default the value of each result is returned. To obtain the normalised path of each result instead, set the result_type parameter to RESULT_TYPE_PATH, or RESULT_TYPE_BOTH can be used to return 2-tuples containing both the value and the path:

from jsonpyth import jsonpath, RESULT_TYPE_BOTH

result = jsonpath(data, '$.biscuits[*].rating', result_type=RESULT_TYPE_BOTH):

for r in result:
    print(r)

Output:

(5, '$["biscuits"][0]["rating"]')
(3.5, '$["biscuits"][1]["rating"]')
(None, '$["biscuits"][2]["rating"]')

Python Expressions

A JSONPath script expression (enclosed in parentheses (...) ) can be used to evaluate a Python statement to provide a dictionary key as a string, or list index as a number. Return values of other types will be ignored.

As parentheses are used to delimit the expression, parentheses used in the script itself must be escaped with a backslash \.

The special symbols @ (current node) and $ (root node) will be substituted for variables named __current and __root respectively, using a simple text replacement before the statement is evaluated. To use a literal @ or $ in the script, it must be escaped with two backslashes \\. Note that a string literal will recognise \\ as an escaped backslash; in such a case each backslash must be further escaped ("\\\\@") or else a raw literal used (r"\\@").

An example script expression:

result = jsonpath(data, r'$.cakes[(len\(@\)-1)].name')

for r in result:
    print(r)

Output:

jaffa cakes

NOTE JSONPyth calls eval to evaluate Python script, and so is unsafe to use for JSONPath expressions from untrusted sources.

Python Filters

Similar to expressions, filters ( ?(...) ) use a Python statement to test whether to include a node or not. The truthiness of the resulting value will be tested using bool, and if False the node will be omitted.

Example:

result = jsonpath(data, r'$[*][?(@["name"].startswith\("b"\))]')

for r in result:
    print(r)

Output:

{"name": "battenberg"}
{"name": "bourbon", "rating": 5}

Credits and Licence

JSONPyth was written by Mark Frimston and is licenced using the the MIT licence. The full text of this licence can be found in the LICENCE.txt file.

Project details


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