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Editorial Team
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Asked: 2026-05-28T01:05:13+00:00

I am trying to write a simple (lightweight) RESTful server in Python. I have

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I am trying to write a simple (lightweight) RESTful server in Python. I have come across the following code from Google:

import web
import json
from mimerender import mimerender

render_xml = lambda message: '<message>%s</message>'%message
render_json = lambda **args: json.dumps(args)
render_html = lambda message: '<html><body>%s</body></html>'%message
render_txt = lambda message: message

urls = (
    '/(.*)', 'greet'
)
app = web.application(urls, globals())

class greet:
    @mimerender(
        default = 'html',
        html = render_html,
        xml  = render_xml,
        json = render_json,
        txt  = render_txt
    )
    def GET(self, name):
        if not name: 
            name = 'world'
        return {'message': 'Hello, ' + name + '!'}

if __name__ == "__main__":
    app.run()

I am unfamiliar with the syntax used on the line @mimerender. This appears to be a a weird combination of a constructor and a function decorator – however, all uses of decorators I have encountered to date are typically written like this:

def foo():
    pass

def foobar():
    pass

@foo
@pass
def some_other_func():
    pass

What does the @mimerender section of the code mean/do?

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1 Answer

  1. Editorial Team
    @expr
def foo(args):
    pass

    is equivalent to

    def foo(args):
    pass
foo = expr(foo)

    expr can be any valid python expression, so what happens here is that mimerender(…) returns a callable object (either by being a constructor or by being a function that returns a callable object). Not much magic around here 🙂

    The above call is thus just

    def GET(self, name):
    if not name: 
        name = 'world'
    return {'message': 'Hello, ' + name + '!'}
GET = mimerender(…)(GET)
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