An easy method for getting attribute information from the PSSE subsystem data retrieval api

subsystem_info.py

from itertools import groupby
from operator import itemgetter
attr_type = itemgetter(0)

import psspy

def subsystem_info(name, attributes, sid=-1, inservice=True):
    """
    Returns requested attributes from the PSS(r)E subsystem API
    for the given subsystem id and subsystem element name.

    e.g. to retrieve bus attributes "NAME", "NUMBER" and "PU"
      
      subsystem_info('bus', ["NAME", "NUMBER", "PU"])

    where the 'bus' `name` argument comes from the original
    PSS(r)E subsystem API naming convention found in Chapter 8 of the
    PSS(r)E API.

    abusint  # bus
    amachint # mach
    aloadint # load

    Args:
      inservice [optional]: True (default) to list only information
         for in service elements;
      sid [optional]: list only information for elements in this
         subsystem id (-1, all elements by default).  
    
    """
    name = name.lower()
    gettypes = getattr(psspy, 'a%stypes' % name)
    apilookup = {
            'I': getattr(psspy, 'a%sint' % name),
            'R': getattr(psspy, 'a%sreal' % name),
            'X': getattr(psspy, 'a%scplx' % name),
            'C': getattr(psspy, 'a%schar' % name), }

    result = []
    ierr, attr_types = gettypes(attributes)

    for k, group in groupby(zip(attr_types, attributes), key=attr_type):
        func = apilookup[k]
        strings = list(zip(*group)[1])
        ierr, res = func(sid, flag=1 if inservice else 2, string=strings)
        result.extend(res)

    return zip(*result)