Support Float type

[ChristianKuehnel]

If would be nice, if pysnmp would support the Float data type out of the box: https://tools.ietf.org/html/draft-perkins-opaque-01

For Home Assistant I implemented a workaround:
https://github.com/ChristianKuehnel/home-assistant/blob/b8cf07e116d539767503c7c73ead0ef6399a4107/homeassistant/components/sensor/snmp.py#L195

But this is not the most elegant solution. It would be nice, if that type would be available as part of pysnmp.

If you're looking for a test case: The system load in snmpd is a Float

[etingof]

Thank you for rising this FR! It totally makes sense to me.

It is not hard to code up, however I need to think how to fit this second-stage Opaque payload en/decoding within the existing API.