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jq.py: a lightweight and flexible JSON processor
================================================
This project contains Python bindings for
`jq <http://stedolan.github.io/jq/>`_.
Installation
------------
Wheels are built for various Python versions and architectures on Linux and Mac OS X.
On these platforms, you should be able to install jq with a normal pip install:
.. code-block:: sh
pip install jq
If a wheel is not available,
the source for jq 1.6 is downloaded over HTTPS and built.
This requires:
* Autoreconf
* The normal C compiler toolchain, such as gcc and make.
* libtool
* Python headers.
Debian, Ubuntu or relatives
~~~~~~~~~~~~~~~~~~~~~~~~~~~
If on Debian, Ubuntu or relatives, running the following command should be sufficient:
.. code-block:: sh
apt-get install autoconf automake build-essential libtool python-dev
Red Hat, Fedora, CentOS or relatives
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If on Red Hat, Fedora, CentOS, or relatives, running the following command should be sufficient:
.. code-block:: sh
yum groupinstall "Development Tools"
yum install autoconf automake libtool python python-devel
Mac OS X
~~~~~~~~
If on Mac OS X, you probably want to install
`Xcode <https://developer.apple.com/xcode/>`_ and `Homebrew <http://brew.sh/>`_.
Once Homebrew is installed, you can install the remaining dependencies with:
.. code-block:: sh
brew install autoconf automake libtool
Usage
-----
Using jq requires three steps:
#. Call ``jq.compile()`` to compile a jq program.
#. Call an input method on the compiled program to supply the input.
#. Call an output method on the result to retrieve the output.
For instance:
.. code-block:: python
import jq
assert jq.compile(".+5").input_value(42).first() == 47
Input methods
~~~~~~~~~~~~~
Call ``.input_value()`` to supply a valid JSON value, such as the values returned from ``json.load``:
.. code-block:: python
import jq
assert jq.compile(".").input_value(None).first() == None
assert jq.compile(".").input_value(42).first() == 42
assert jq.compile(".").input_value(0.42).first() == 0.42
assert jq.compile(".").input_value(True).first() == True
assert jq.compile(".").input_value("hello").first() == "hello"
Call ``.input_values()`` to supply multiple valid JSON values, such as the values returned from ``json.load``:
.. code-block:: python
import jq
assert jq.compile(".+5").input_values([1, 2, 3]).all() == [6, 7, 8]
Call ``.input_text()`` to supply unparsed JSON text:
.. code-block:: python
import jq
assert jq.compile(".").input_text("null").first() == None
assert jq.compile(".").input_text("42").first() == 42
assert jq.compile(".").input_text("0.42").first() == 0.42
assert jq.compile(".").input_text("true").first() == True
assert jq.compile(".").input_text('"hello"').first() == "hello"
assert jq.compile(".").input_text("1\n2\n3").all() == [1, 2, 3]
Pass ``slurp=True`` to ``.input_text()`` to read the entire input into an array:
.. code-block:: python
import jq
assert jq.compile(".").input_text("1\n2\n3", slurp=True).first() == [1, 2, 3]
You can also call the older ``input()`` method by passing:
* a valid JSON value, such as the values returned from ``json.load``, as a positional argument
* unparsed JSON text as the keyword argument ``text``
For instance:
.. code-block:: python
import jq
assert jq.compile(".").input("hello").first() == "hello"
assert jq.compile(".").input(text='"hello"').first() == "hello"
Return methods
~~~~~~~~~~~~~~
Calling ``first()`` on the result will run the program with the given input,
and return the first output element.
.. code-block:: python
import jq
assert jq.compile(".").input_value("hello").first() == "hello"
assert jq.compile("[.[]+1]").input_value([1, 2, 3]).first() == [2, 3, 4]
assert jq.compile(".[]+1").input_value([1, 2, 3]).first() == 2
Call ``text()`` instead of ``first()`` to serialise the output into JSON text:
.. code-block:: python
assert jq.compile(".").input_value("42").text() == '"42"'
When calling ``text()``, if there are multiple output elements, each element is represented by a separate line:
.. code-block:: python
assert jq.compile(".[]").input_value([1, 2, 3]).text() == "1\n2\n3"
Call ``all()`` to get all of the output elements in a list:
.. code-block:: python
assert jq.compile(".[]+1").input_value([1, 2, 3]).all() == [2, 3, 4]
Call ``iter()`` to get all of the output elements as an iterator:
.. code-block:: python
iterator = iter(jq.compile(".[]+1").input_value([1, 2, 3]))
assert next(iterator, None) == 2
assert next(iterator, None) == 3
assert next(iterator, None) == 4
assert next(iterator, None) == None
Arguments
~~~~~~~~~
Calling ``compile()`` with the ``args`` argument allows predefined variables to be used within the program:
.. code-block:: python
program = jq.compile("$a + $b + .", args={"a": 100, "b": 20})
assert program.input_value(3).first() == 123
Convenience functions
~~~~~~~~~~~~~~~~~~~~~
Convenience functions are available to get the output for a program and input in one call:
.. code-block:: python
assert jq.first(".[] + 1", [1, 2, 3]) == 2
assert jq.first(".[] + 1", text="[1, 2, 3]") == 2
assert jq.text(".[] + 1", [1, 2, 3]) == "2\n3\n4"
assert jq.all(".[] + 1", [1, 2, 3]) == [2, 3, 4]
assert list(jq.iter(".[] + 1", [1, 2, 3])) == [2, 3, 4]
Original program string
~~~~~~~~~~~~~~~~~~~~~~~
The original program string is available on a compiled program as the ``program_string`` attribute:
.. code-block:: python
program = jq.compile(".")
assert program.program_string == "."
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