MIME Type helpers

This helper depends on the WebOb package, and has optional Pylons support.

class webhelpers.mimehelper.MIMETypes(environ)

MIMETypes registration mapping

The MIMETypes object class provides a single point to hold onto all the registered mimetypes, and their association extensions. It’s used by the mimetypes method to determine the appropriate content type to return to a client.

classmethod add_alias(alias, mimetype)

Create a MIMEType alias to a full mimetype.


  • add_alias('html', 'text/html')
  • add_alias('xml', 'application/xml')

An alias may not contain the / character.

aliases = {}
classmethod init()

Loads a default mapping of extensions and mimetypes

These are suitable for most web applications by default. Additional types can be added by using the mimetypes module.


Check the PATH_INFO of the current request and client’s HTTP Accept to attempt to use the appropriate mime-type.

If a content-type is matched, return the appropriate response content type, and if running under Pylons, set the response content type directly. If a content-type is not matched, return False.

This works best with URLs that end in extensions that differentiate content-type. Examples: http://example.com/example, http://example.com/example.xml, http://example.com/example.csv

Since browsers generally allow for any content-type, but should be sent HTML when possible, the html mimetype check should always come first, as shown in the example below.


# some code likely in environment.py
MIMETypes.add_alias('html', 'text/html')
MIMETypes.add_alias('xml', 'application/xml')
MIMETypes.add_alias('csv', 'text/csv')

# code in a Pylons controller
def someaction(self):
    # prepare a bunch of data
    # ......
    # prepare MIMETypes object
    m = MIMETypes(request.environ)
    if m.mimetype('html'):
        return render('/some/template.html')
    elif m.mimetype('atom'):
        return render('/some/xml_template.xml')
    elif m.mimetype('csv'):
        # write the data to a csv file
        return csvfile

# Code in a non-Pylons controller.
m = MIMETypes(environ)
response_type = m.mimetype('html')
# ``response_type`` is a MIME type or ``False``.