JMESPath
========
JMESPath (pronounced "jaymz path") allows you to declaratively specify how to
extract elements from a JSON document.
For example, given this document::
{"foo": {"bar": "baz"}}
The jmespath expression ``foo.bar`` will return "baz".
JMESPath also supports:
Referencing elements in a list. Given the data::
{"foo": {"bar": ["one", "two"]}}
The expression: ``foo.bar[0]`` will return "one".
You can also reference all the items in a list using the ``*``
syntax::
{"foo": {"bar": [{"name": "one"}, {"name": "two"}]}}
The expression: ``foo.bar[*].name`` will return ["one", "two"].
Negative indexing is also supported (-1 refers to the last element
in the list). Given the data above, the expression
``foo.bar[-1].name`` will return "two".
The ``*`` can also be used for hash types::
{"foo": {"bar": {"name": "one"}, "baz": {"name": "two"}}}
The expression: ``foo.*.name`` will return ["one", "two"].
**NOTE: jmespath is being actively developed. There are a number
of features it does not currently support that may be added in the
future.**
Specification
=============
The grammar is specified using ABNF, as described in `RFC4234`_.
You can find the most up to date grammar for JMESPath
`here <http://jmespath.readthedocs.org/en/latest/specification.html#grammar>`__.
You can read the full JMESPath specification
`here http://jmespath.readthedocs.org/en/latest/specification.html`__.
Testing
=======
In addition to the unit tests for the jmespath modules,
there is a ``tests/compliance`` directory that contains
.json files with test cases. This allows other implementations
to verify they are producing the correct output. Each json
file is grouped by feature.
Python Library
==============
The included python implementation has two convenience functions
that operate on python data structures. You can use ``search``
and give it the jmespath expression and the data::
>>> import jmespath
>>> path = jmespath.search('foo.bar', {'foo': {'bar': 'baz'}})
'baz'
Similar to the ``re`` module, you can store the compiled expressions
and reuse them to perform repeated searches::
>>> import jmespath
>>> path = jmespath.compile('foo.bar')
>>> path.search({'foo': {'bar': 'baz'}})
'baz'
>>> path.search({'foo': {'bar': 'other'}})
'other'
You can also use the ``jmespath.parser.Parser`` class directly
if you want more control.
Updating the Grammar
====================
If you are updating the grammar in ``parser.py`` you'll need to run
``bin/gen-tables`` on both python2 and python3 to update the
``jmespath/_lrtable.py`` and ``jmespath/_lrtable3.py`` files.
.. _RFC4234: http://tools.ietf.org/html/rfc4234
========
JMESPath (pronounced "jaymz path") allows you to declaratively specify how to
extract elements from a JSON document.
For example, given this document::
{"foo": {"bar": "baz"}}
The jmespath expression ``foo.bar`` will return "baz".
JMESPath also supports:
Referencing elements in a list. Given the data::
{"foo": {"bar": ["one", "two"]}}
The expression: ``foo.bar[0]`` will return "one".
You can also reference all the items in a list using the ``*``
syntax::
{"foo": {"bar": [{"name": "one"}, {"name": "two"}]}}
The expression: ``foo.bar[*].name`` will return ["one", "two"].
Negative indexing is also supported (-1 refers to the last element
in the list). Given the data above, the expression
``foo.bar[-1].name`` will return "two".
The ``*`` can also be used for hash types::
{"foo": {"bar": {"name": "one"}, "baz": {"name": "two"}}}
The expression: ``foo.*.name`` will return ["one", "two"].
**NOTE: jmespath is being actively developed. There are a number
of features it does not currently support that may be added in the
future.**
Specification
=============
The grammar is specified using ABNF, as described in `RFC4234`_.
You can find the most up to date grammar for JMESPath
`here <http://jmespath.readthedocs.org/en/latest/specification.html#grammar>`__.
You can read the full JMESPath specification
`here http://jmespath.readthedocs.org/en/latest/specification.html`__.
Testing
=======
In addition to the unit tests for the jmespath modules,
there is a ``tests/compliance`` directory that contains
.json files with test cases. This allows other implementations
to verify they are producing the correct output. Each json
file is grouped by feature.
Python Library
==============
The included python implementation has two convenience functions
that operate on python data structures. You can use ``search``
and give it the jmespath expression and the data::
>>> import jmespath
>>> path = jmespath.search('foo.bar', {'foo': {'bar': 'baz'}})
'baz'
Similar to the ``re`` module, you can store the compiled expressions
and reuse them to perform repeated searches::
>>> import jmespath
>>> path = jmespath.compile('foo.bar')
>>> path.search({'foo': {'bar': 'baz'}})
'baz'
>>> path.search({'foo': {'bar': 'other'}})
'other'
You can also use the ``jmespath.parser.Parser`` class directly
if you want more control.
Updating the Grammar
====================
If you are updating the grammar in ``parser.py`` you'll need to run
``bin/gen-tables`` on both python2 and python3 to update the
``jmespath/_lrtable.py`` and ``jmespath/_lrtable3.py`` files.
.. _RFC4234: http://tools.ietf.org/html/rfc4234
Release files for jmespath 0.3.1
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