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The HTTPRequest class in the tornado* web framework helpfully maps GET and POST arguments to lists. I understand why -- in case a given argument name is used multiple times. But for some RequestHandlers, this is a pain. For instance, if I want to pass a json object and parse it as-is on the server.

What's the most straightforward way to disable the map-to-list behavior so that I can send unaltered json to a tornado/cyclone server?

*Cyclone, actually, in case there's an implementation difference here.

Abe
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2 Answers2

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Instead of accessing self.request.arguments directly you should use the accessor functions:

self.get_argument("ID", default=None, strip=False)

This returns a single item.

If you want to turn the arguments into a JSON object you can quite easily do so: 

json.dumps({ k: self.get_argument(k) for k in self.request.arguments })
Glycerine
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koblas
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  • Thanks! What if I just want to return the whole set of arguments as a single json object? I could reconstruct it by iterating over the whole dictionary and calling get_argument for each key, but that seems inefficient. – Abe Apr 28 '12 at 01:05
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    json.dumps({ k: self.get_argument(k) for k in self.request.arguments }) - it's not really that inefficient. – koblas Apr 28 '12 at 13:39
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I'm going to go with "you're out of luck." You could re-write the class in question (looks like that would not be fun), but aside from that I don't see many options.

I would just use a dict comprehension.

{k:''.join(v) for k,v in  self.request.arguments.iteritems()}
Diroshi Fernando
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cwallenpoole
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