How to return a structured empty list

[bard5216]

I have created a textfsm template for cisco_ios "show port-security" and it works for the case where a show port-security returns interface rows but if there are no interface rows it just returns the raw output. This seems to me that it is a failed condition and what I would like to see is an empty list.

My template looks like:

Value PORT (\S+)
Value MAX_ADDR_COUNT (\d+)
Value CURRENT_ADDR_COUNT (\d+)
Value VIOLATION_COUNT (\d+)
Value ACTION ([Pp]rotect|[Rr]estrict|[Ss]hutdown)

Start
  ^Secure Port
  ^\s+.*Count
  ^---+$$ -> Ports 
  ^. -> Error

Ports
  ^\s*${PORT}\s+${MAX_ADDR_COUNT}\s+${CURRENT_ADDR_COUNT}\s+${VIOLATION_COUNT}\s+${ACTION}$$ -> Record
  ^---+ -> End
  ^. -> Error

This output will parse correctly:

out = """Secure Port  MaxSecureAddr  CurrentAddr  SecurityViolation  Security Action
                (Count)       (Count)          (Count)
---------------------------------------------------------------------------
    Gi1/0/1             12            1                  0         Restrict
    Gi1/0/2             12            1                  0         Restrict
---------------------------------------------------------------------------
Total Addresses in System (excluding one mac per port)     : 2
Max Addresses limit in System (excluding one mac per port) : 4096"""

This output will not parse correctly:

out = """Secure Port  MaxSecureAddr  CurrentAddr  SecurityViolation  Security Action
                (Count)       (Count)          (Count)
---------------------------------------------------------------------------
---------------------------------------------------------------------------
Total Addresses in System (excluding one mac per port)     : 0
Max Addresses limit in System (excluding one mac per port) : 8192"""

I looked at the Netmiko code and I think this is determined in netmiko.utilities.get_structured_data()

    try:
        # Parse output through template
        textfsm_obj.ParseCmd(raw_output, attrs)
        structured_data = clitable_to_dict(textfsm_obj)
        output = raw_output if structured_data == [] else structured_data
        return output
    except CliTableError:
        return raw_output

textfsm.ParseCmd() does return an empty list.

Any advice on how I should handle this situation?

Thanks,
Barry

[ktbyers]

You would probably have to just code it into Netmiko i.e.

if isinstance(output, str):
    output = []

Or you could bypass Netmiko's built-in use_textfsm=True to send_command and do the conversion yourself (i.e. recreate that function and drop the empty list check).