bc-jsonpath-ng 1.6.1

A final implementation of JSONPath for Python that aims to be standard compliant, including arithmetic and binary comparison operators and providing clear AST for metaprogramming.

A final implementation of JSONPath for Python that aims to be standard compliant, including arithmetic and binary comparison operators, as defined in the original JSONPath proposal.

This packages merges both jsonpath-rw and jsonpath-rw-ext and provides several AST API enhancements, such as the ability to update or removes nodes in the tree.

About

This library provides a robust and significantly extended implementation of JSONPath for Python.

This library differs from other JSONPath implementations in that it is a full language implementation, meaning the JSONPath expressions are first class objects, easy to analyze, transform, parse, print, and extend.

Quick Start

To install, use pip:

$ pip install --upgrade jsonpath-ng

Usage

Basic examples:

$ python

>>> from jsonpath_ng import jsonpath, parse

# A robust parser, not just a regex. (Makes powerful extensions possible; see below)
>>> jsonpath_expr = parse('foo[*].baz')

# Extracting values is easy
>>> [match.value for match in jsonpath_expr.find({'foo': [{'baz': 1}, {'baz': 2}]})]
[1, 2]

# Matches remember where they came from
>>> [str(match.full_path) for match in jsonpath_expr.find({'foo': [{'baz': 1}, {'baz': 2}]})]
['foo.[0].baz', 'foo.[1].baz']

# And this can be useful for automatically providing ids for bits of data that do not have them (currently a global switch)
>>> jsonpath.auto_id_field = 'id'
>>> [match.value for match in parse('foo[*].id').find({'foo': [{'id': 'bizzle'}, {'baz': 3}]})]
['foo.bizzle', 'foo.[1]']

# A handy extension: named operators like `parent`
>>> [match.value for match in parse('a.*.b.`parent`.c').find({'a': {'x': {'b': 1, 'c': 'number one'}, 'y': {'b': 2, 'c': 'number two'}}})]
['number two', 'number one']

# You can also build expressions directly quite easily
>>> from jsonpath_ng.jsonpath import Fields
>>> from jsonpath_ng.jsonpath import Slice

>>> jsonpath_expr_direct = Fields('foo').child(Slice('*')).child(Fields('baz'))  # This is equivalent

Using the extended parser:

$ python

>>> from jsonpath_ng.ext import parse

# A robust parser, not just a regex. (Makes powerful extensions possible; see below)
>>> jsonpath_expr = parse('foo[*].baz')

JSONPath Syntax

The JSONPath syntax supported by this library includes some additional features and omits some problematic features (those that make it unportable). In particular, some new operators such as | and where are available, and parentheses are used for grouping not for callbacks into Python, since with these changes the language is not trivially associative. Also, fields may be quoted whether or not they are contained in brackets.

Atomic expressions:

Syntax	Meaning
$	The root object
`this`	The “current” object.
`foo`	More generally, this syntax allows “named operators” to extend JSONPath is arbitrary ways
field	Specified field(s), described below
[ field ]	Same as field
[ idx ]	Array access, described below (this is always unambiguous with field access)

Jsonpath operators:

Syntax	Meaning
jsonpath1 . jsonpath2	All nodes matched by jsonpath2 starting at any node matching jsonpath1
jsonpath [ whatever ]	Same as jsonpath.whatever
jsonpath1 .. jsonpath2	All nodes matched by jsonpath2 that descend from any node matching jsonpath1
jsonpath1 where jsonpath2	Any nodes matching jsonpath1 with a child matching jsonpath2
jsonpath1 | jsonpath2	Any nodes matching the union of jsonpath1 and jsonpath2

Field specifiers ( field ):

Syntax	Meaning
fieldname	the field fieldname (from the “current” object)
"fieldname"	same as above, for allowing special characters in the fieldname
'fieldname'	ditto
*	any field
field , field	either of the named fields (you can always build equivalent jsonpath using |)

Array specifiers ( idx ):

Syntax	Meaning
[n]	array index (may be comma-separated list)
[start?:end?]	array slicing (note that step is unimplemented only due to lack of need thus far)
[*]	any array index

Programmatic JSONPath

If you are programming in Python and would like a more robust way to create JSONPath expressions that does not depend on a parser, it is very easy to do so directly, and here are some examples:

• Root()

• Slice(start=0, end=None, step=None)

• Fields('foo', 'bar')

• Index(42)

• Child(Fields('foo'), Index(42))

• Where(Slice(), Fields('subfield'))

• Descendants(jsonpath, jsonpath)

Extras

• Path data: The result of JsonPath.find provide detailed context and path data so it is easy to traverse to parent objects, print full paths to pieces of data, and generate automatic ids.

• Automatic Ids: If you set jsonpath_ng.auto_id_field to a value other than None, then for any piece of data missing that field, it will be replaced by the JSONPath to it, giving automatic unique ids to any piece of data. These ids will take into account any ids already present as well.

• Named operators: Instead of using @ to reference the currently object, this library uses `this`. In general, any string contained in backquotes can be made to be a new operator, currently by extending the library.

Extensions

name	Example
len	$.objects.`len`
sub	$.field.`sub(/foo\\+(.*)/, \\1)`
split	$.field.`split(+, 2, -1)` $.field.`split(sep, segement, maxsplit)`
sorted	$.objects.`sorted` $.objects[\some_field] $.objects[\some_field,/other_field]
filter	$.objects[?(@some_field > 5)] $.objects[?some_field = “foobar”)] $.objects[?some_field =~ “foobar”)] $.objects[?some_field > 5 & other < 2)]
arithmetic (-+*/)	$.foo + “_” + $.bar $.foo * 12 $.objects[*].cow + $.objects[*].cat

About arithmetic and string

Operations are done with python operators and allows types that python allows, and return [] if the operation can be done due to incompatible types.

When operators are used, a jsonpath must be be fully defined otherwise jsonpath-rw-ext can’t known if the expression is a string or a jsonpath field, in this case it will choice string as type.

Example with data:

{
    'cow': 'foo',
    'fish': 'bar'
}

cow + fish returns cowfish

$.cow + $.fish returns foobar

$.cow + “_” + $.fish returns foo_bar

$.cow + “_” + fish returns foo_fish

About arithmetic and list

Arithmetic can be used against two lists if they have the same size.

Example with data:

{'objects': [
    {'cow': 2, 'cat': 3},
    {'cow': 4, 'cat': 6}
]}

$.objects[*].cow + $.objects[*].cat returns [6, 9]

More to explore

There are way too many JSONPath implementations out there to discuss. Some are robust, some are toy projects that still work fine, some are exercises. There will undoubtedly be many more. This one is made for use in released, maintained code, and in particular for programmatic access to the abstract syntax and extension. But JSONPath at its simplest just isn’t that complicated, so you can probably use any of them successfully. Why not this one?

The original proposal, as far as I know:

• JSONPath - XPath for JSON by Stefan Goessner.

Other examples

Loading json data from file

import json
d = json.loads('{"foo": [{"baz": 1}, {"baz": 2}]}')
# or
with open('myfile.json') as f:
    d = json.load(f)

Special note about PLY and docstrings

The main parsing toolkit underlying this library, PLY, does not work with docstrings removed. For example, PYTHONOPTIMIZE=2 and python -OO will both cause a failure.

Contributors

This package was authored by:

• Kenn Knowles

• Tomas Aparicio

with the help of patches submitted by these contributors.

Copyright and License

Copyright 2013 - Kenneth Knowles

Copyright 2017 - Tomas Aparicio

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.