DoJSON is a simple Pythonic JSON to JSON converter.
DoJSON is on PyPI so all you need is:
$ pip install dojson
Documentation is readable at https://dojson.readthedocs.io/ or it can be built using Sphinx:
$ pip install dojson[docs]
$ python setup.py build_sphinx
Running the test suite is as simple as:
$ python setup.py test
A simple example on how to convert MARCXML to JSON:
from dojson.contrib.marc21.utils import create_record, split_stream
from dojson.contrib.marc21 import marc21
[marc21.do(create_record(data)) for data in split_stream(open('/tmp/data.xml', 'r'))]