Skip to main content
This is a pre-production deployment of Warehouse. Changes made here affect the production instance of PyPI (
Help us improve Python packaging - Donate today!

Coercing data into a normalized form

Project Description

This library provides functions that coerce datastructures into normalized forms. For example, converting an arbitrary dict into a form that is suitable for passing to json.dumps.

The tornado framework has a function called recursive_unicode in the tornado.escape module. It is a very simple recursive walk of datastructure that switches on type and transforms string values into unicode strings. I use this in production software regularly and it works like a charm. Or at least it did until my software encountered a deeply nested dictionary and I received a RuntimeError: maximum recursion depth exceeded error in my service log. This is one of the exceptions that strikes fear into most engineers when it rears it’s head in production.

That is the primary reason for this library existing. It provides the same simple string encoding function iteratively instead of recursively. At the same time, the need to coerce values into a normalized string form is something that I’ve had to do repeatedly so it might as well be plopped into a reusable library.


The following example shows one of the underlying reasons that this library was created. The commonly used msgpack implementation for python returns everything as byte strings which is problematic if you want to dump it as JSON since it will raise a TypeError if dictionary keys are not strings. (This is where recursive_unicode was so handy.)

>>> import json
>>> import coercion
>>> import msgpack
>>> bin_msg = msgpack.packb({u'\u00DCnicode': b'bytes', b'bytes': 'str'})
>>> decoded = msgpack.unpackb(bin_msg)
>>> decoded
{b'bytes': b'str', b'\xc3\x9cnicode': b'bytes'}
>>> json.dumps(decoded)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/daveshawley/opt/lib/python3.5/json/", line 230, in dumps
    return _default_encoder.encode(obj)
  File "/Users/daveshawley/opt/lib/python3.5/json/", line 199, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/Users/daveshawley/opt/lib/python3.5/json/", line 257, in iterencode
    return _iterencode(o, 0)
TypeError: keys must be a string
>>> json.dumps(coercion.normalize_collection(decoded))
'{"bytes": "str", "\\u00dcnicode": "bytes"}'
Release History

Release History

This version
History Node


History Node


Download Files

Download Files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

File Name & Checksum SHA256 Checksum Help Version File Type Upload Date
coercion-1.0.0-py2.py3-none-any.whl (7.0 kB) Copy SHA256 Checksum SHA256 py2.py3 Wheel Nov 2, 2015
coercion-1.0.0.tar.gz (7.9 kB) Copy SHA256 Checksum SHA256 Source Nov 2, 2015

Supported By

WebFaction WebFaction Technical Writing Elastic Elastic Search Pingdom Pingdom Monitoring Dyn Dyn DNS Sentry Sentry Error Logging CloudAMQP CloudAMQP RabbitMQ Heroku Heroku PaaS Kabu Creative Kabu Creative UX & Design Fastly Fastly CDN DigiCert DigiCert EV Certificate Rackspace Rackspace Cloud Servers DreamHost DreamHost Log Hosting