SNMP Toolkit

[popov]

Have you tried yapsnmp: http://yapsnmp.sourceforge.net/ ?
It is a Python wrapper around net-snmp, so should be fast.
It also claims to be thread-safe.
The problem you could have is that it's advertised as a posix module
only. But the wrapper is built using SWIG, so it should be possible to
build it for Windows without too much hassle.
Note that I've never used it myself, so can't comment on the package
itself.
However, I will have to do some snmp coding soon, and it's the first
one I will try.