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Flask-Holster 0.3.4

Rigid MVC content negotiation for Flask

This is Holster, an extension for Flask that makes RESTfulness and content negotiation easy:

from flask import Flask
from flask.ext.holster.main import init_holster

app = Flask(__name__)

def test():
    from math import pi

    return {
        "data": "Hello from Holster!",
        "nested": {
            "numeric": 0,
            "floating": pi,
            "unicode": u"Espa\xf1ol",
        "secure": {
            "xss-sword": ';!--"<XSS>=&{()}',

if __name__ == "__main__":

This application will automatically figure out which data type to return, using a combination of user agent parameters and URL extensions. If a user agent requests “/test.html” they will get HTML, but if they request “/test.json” they will get JSON instead. No longer do you have to worry about constructing sites with separate interfaces for HTML and JSON; one holstered site can do it all!

Holster currently has default renderers for the following formats:

  • HTML
  • JSON
  • Plaintext
  • YAML (with optional PyYAML support for prettified YAML)

These default renderers are provided mostly for bootstrapping and development, although the JSON and YAML renderers are likely very similar to the renderers that one might desire in production.



  • Feature: The JSON renderer can render custom objects if they implement a __json__ method for reducing to JSON-safe objects.


  • Bugfix: Multiple holsterings of a single view in Flask 0.10 and newer were causing Flask to refuse to register views due to an internal assertion being triggered.
  • Feature: The "title" key now holds special significance: it will be used for titles in built-in renderers, if the renderer supports the notion of a title.


  • Bugfix: Custom templaters were being incorrectly unused if they were not HTML or JSON templaters.
  • Feature: Allow “svg” as an extension for the “image/svg+xml” MIME type.


  • Bugfix: Remove extraneous debugging statements.


  • Compatibility: Require vcversioner for version numbers.
  • Compatibility: The handwritten MIME parser has been removed in favor of the one in Werkzeug. As a result, Flask-Holster is slightly smaller and should handle corner cases slightly better.
  • Bugfix: Always define a YAML conversion. For pretty YAML, install PyYAML. YAML output is now always enabled, using JSON as a fallback when PyYAML is not available. PyYAML is not required and is not in the requirements.txt.


  • Feature: init_holster() now works on Flask blueprints as well as Flask applications.


  • Bugfix: Correctly omit trailing colons (and related recursion) on list items in the default HTML view template.


  • Bugfix: Permit kwargs in routing decorators, including methods.
  • Bugfix: Pass along premade responses as-is without any interference. Permits things like redirect() inside otherwise-rigid controllers.


  • Bugfix: Pass along names inside lift() to correctly name reversed routes


  • Bugfix: Specialize extended routes for “/” to avoid malformed routes


  • Compatibility: Don’t use itertools, for Python 2.5
  • Enhancement: Split holsterizing views into two pieces, for easier customization
  • Feature: New helpers module for helping write customized views


  • Feature: Changelog
  • Feature: Documentation
  • Feature: Optional HOLSTER_COMPRESS setting for automatically compressing response data
  • Enhancement: Vary header is filled out
  • Change: Improved names of view objects
File Type Py Version Uploaded on Size
Flask-Holster-0.3.4.tar.gz (md5) Source 2013-08-12 7KB