Best way to encode tuples with json

Question

In python I have a dictionary that maps tuples to a list of tuples. e.g.

{(1,2): [(2,3),(1,7)]}

I want to be able to encode this data use it with javascript, so I looked into json but it appears keys must be strings so my tuple does not work as a key.

Is the best way to handle this is encode it as "1,2" and then parse it into something I want on the javascript? Or is there a more clever way to handle this.

Answer 1

You might consider saying

{"[1,2]": [(2,3),(1,7)]} 

and then when you need to get the value out, you can just parse the keys themselves as JSON objects, which all modern browsers can do with the built-in JSON.parse method (I'm using jQuery.each to iterate here but you could use anything):

var myjson = JSON.parse('{"[1,2]": [[2,3],[1,7]]}'); $.each(myjson, function(keystr,val){     var key = JSON.parse(keystr);     // do something with key and val }); 

On the other hand, you might want to just structure your object differently, e.g.

{1: {2: [(2,3),(1,7)]}} 

so that instead of saying

myjson[1,2] // doesn't work 

which is invalid Javascript syntax, you could say

myjson[1][2] // returns [[2,3],[1,7]] 

Answer 2

If your key tuples are truly integer pairs, then the easiest and probably most straightforward approach would be as you suggest.... encode them to a string. You can do this in a one-liner:

>>> simplejson.dumps(dict([("%d,%d" % k, v) for k, v in d.items()])) '{"1,2": [[2, 3], [1, 7]]}' 

This would get you a javascript data structure whose keys you could then split to get the points back again:

'1,2'.split(',')