argument checking before getattr

[Jason Orendorff]

> Thank you very much for the reply. This is a different level of
> understanding. How do you find these information?

I recommend the Python tutorial.
  http://www.python.org/doc/current/tut/tut.html

Section 9.3.4 covers method objects.

http://www.python.org/doc/current/tut/node11.html#SECTION0011340000000000000
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## Jason Orendorff    http://www.jorendorff.com/