pysnmp-lextudio using next() with the getCmd() generator leads to TypeError: 'tuple' object is not an iterator

Question

I have removed pysnmp and installed pysnmp-lextudio in an attempt to bring my codebase up to python 3.12.2

Code that ran with previous pysnmp versions now returns the error: 'tuple' object is not an iterator

Offending code is next() of last line:

from pysnmp.hlapi import *
g = getCmd(SnmpEngine(),
    CommunityData('community', mpModel=1),
    UdpTransportTarget((ipAddress, port)),
    ContextData(),
    ObjectType(ObjectIdentity('SNMPv2-MIB', 'sysDescr', 0)))
        
errorIndication, errorStatus, errorIndex, varBinds = next(g)

Any insight is welcome, device behaving via snmp walk.

Answer 1

Because whereas the library pynsmp seems to return a generator from the getCmd function (see documentation, the pysnmp-lexstudio already performs the query.

The example from pynsmp-lextudio site:

>>> from pysnmp.hlapi import *
>>> g = getCmd(SnmpEngine(),
...            CommunityData('public'),
...            UdpTransportTarget(('demo.pysnmp.com', 161)),
...            ContextData(),
...            ObjectType(ObjectIdentity('SNMPv2-MIB', 'sysDescr', 0)))
>>> g
(None, 0, 0, [ObjectType(ObjectIdentity(ObjectName('1.3.6.1.2.1.1.1.0')), DisplayString('SunOS zeus.pysnmp.com 4.1.3_U1 1 sun4m'))])

And from the pysnmp documentation:

>>> from pysnmp.hlapi import *
>>> g = getCmd(SnmpEngine(),
...            CommunityData('public'),
...            UdpTransportTarget(('demo.snmplabs.com', 161)),
...            ContextData(),
...            ObjectType(ObjectIdentity('SNMPv2-MIB', 'sysDescr', 0)))
>>> next(g)
(None, 0, 0, [ObjectType(ObjectIdentity(ObjectName('1.3.6.1.2.1.1.1.0')), DisplayString('SunOS zeus.snmplabs.com 4.1.3_U1 1 sun4m'))])

Why this has changed, I don't know, but notice the missing next() on the first example.

In fact, if you do just this:

>>> print(getCmd(SnmpEngine(),
... CommunityData('community', mpModel=1),
... UdpTransportTarget((ipAddress, port)),
... ContextData(),
... ObjectType(ObjectIdentity('SNMPv2-MIB', 'sysDescr', 0))))
(RequestTimedOut('No SNMP response received before timeout'), 0, 0, [])

You notice that the command is immediately called without next.

So tl;dr: in your old version, g is a generator, in the new one it's a response.