jq.py: a lightweight and flexible JSON processor

This project contains Python bindings for jq <http://stedolan.github.io/jq/>_ 1.7.

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 1.7 is built. This requires:

• Autoreconf

• The normal C compiler toolchain, such as gcc and make.

• libtool

• Python headers.

Alternatively, set the environment variable JQPY_USE_SYSTEM_LIBS to 1 when installing the package to use the libjq and libonig versions available on the system rather than building them.

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"

Output 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 == "."