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Monday, November 12, 2012

Maya string attr - 32k limit

Just thought I'd spread this in case anybody else is thinking of using a json string to dump data to an attribute in Maya.

Discovered last week that you can happily set a string attr to any length BUT, and it's a big but, if you subsequently select the textfield (you don't even have to edit it, just select it) then Maya runs a change callback and the string is now clamped to 16bit = 32,767 characters. It was driving me mad last week as I kept getting errors in the json decoder when I tried to read a pose back that I'd serialized to a string on our characterNode. I want to store a zero pose on the Character Node along with some extra data that I'm pushing to a dict, json.dumps is a really nice way to that push that dict to a string and store it and then retrieve it back in it's original form with json.load()

Try it for yourself!
import pymel.core as pCore
Cone=pCore.polyCone()[0]
Cone.addAttr('json_test', dt='string')
data= "x" * 40000
Cone.json_test.set(data)

len(Cone.json_test.get()) #>>40000
Now just open the Attribute Editor and just select the json_test textfield - don't edit it, just select it
len(Cone.json_test.get()) #>>32767
Only thing you can do to stop this truncation is to lock the attr, that way it gets stored correctly and doesn't get truncated.

Mark