################################################################################
#
# File:         pythonutils.py
# RCS:          $Header: /u/testbed/CVSROOT/dldev/src/IBClient/pythonutils.py,v 1.1 1996/09/18 23:38:38 hassan Exp $
# Description:  General utilities that improve life with Python even further
# Author:       Andreas Paepcke, Stanford University
# Created:      Fri Aug  9 12:31:55 1996
# Modified:     Fri Aug  9 13:11:52 1996 (Andreas Paepcke) paepcke@Walrus
# Language:     Python
# Package:      N/A
# Status:       Experimental (Do Not Distribute)
#
# (c) Copyright 1996, Stanford University, all rights reserved.
#
################################################################################

import types

# Given an item and a class (not a string, but the class), return 1 if the item
# is an instance of that class:

def isInstanceOf(item, aClass):
  if (type(item) == types.InstanceType) and\
     (item.__class__ == aClass):
    return(1)
  else:
    return(0)
  
# Return an array of the names of all of aClass' subclasses
# (aClass is a class obj, not a str):

def allSubclassesOf(module, aClass):
  subclasses = []
  for name, value in eval(module).__dict__.items():
    if type(value) == types.ClassType:
      if aClass in value.__bases__:
	subclasses.append(name)
  return(subclasses)


# Given a module name and a class name, return the class object. If the module is
# not currently loaded, it gets imported:

def find_class(module, name):
  env = {}
  try:
    exec 'from %s import %s' % (module, name) in env
  except ImportError:
    raise SystemError, \
	  "Failed to import class %s from module %s" % \
	  (name, module)
  klass = env[name]
  if type(klass) != types.ClassType:
    raise SystemError, \
	  "Imported object %s from module %s is not a class" % \
	  (name, module)
  return klass