How to understand this error and debug

Scripting
1

If i meet the following error in rhino python.
How should I understand it , how to debug and check it?

Runtime error (KeyNotFoundException): KeyError

2

Hi Liu,

Seems like you are trying to access some value within your dictionary, with the key that does not exist in that dictionary. Thus the KeyError.

Check official python website for more information:
https://wiki.python.org/moin/KeyError