Emulating a = x.y and x.y = a, when 'y' is a string

[Bruce Dawson]

I want to do dynamic access to member variables in Python - reading from 
and writing to object member variables based on a member name stored in 
a string. If the member is stored in __dict__ it is easy enough, but 
what if it is emulated with __getattr__, or a property, or __getattribute__?

exec() gives the same behavior, but can cause bad performance if you do 
it a lot, because it has to compile the code. Is there any way to get 
Python to do exactly the same thing as x.y = a and a = x.y, when the 
member name is a string.

The following functions work well enough for normal member variables - 
is there a canonical way of doing this in the generic case?

def GetMemberVariable(object, attributeName):
     return object.__dict__[attributeName]

def SetMemberVariable(object, attributeName, newValue):
     object.__dict__[attributeName] = newValue

# Sample usage:
a = GetMemberVariable(x, "y")
SetMemberVariable(x, "y", 0)

Thanks for any help.

Bruce Dawson