Wrapping an object in Python

Question

I am currently trying to write a python wrapper for a project that use non native python calls, to be able to run it in native python.

The code is normally ran into a software that expose additionals non native objects and function that can be used in the python code. I am using win32com.client to connect to the software to retrieve its non native objects and functions, and expose them in my native python code.

As I cannot change change the source code, with it's custom calls to the software, I am trying to write a wrapper.

I have a piece of code that looks like this:

Variable.VariableByName["myVariableName"] = myVariableValue

This code is supposed to edit the attribute myVariableName of the object Variable and set it to myVariableValue. VariableByName, in native python, is seen as a function, and cannot be called via "VariableByName["myVariableName"]".

I have created this wrapper, but I cannot figure how to retrieve the myVariableName and the myVariableValue in the wrapper...

class VariableWrap():
    def __init__(self, object):
        global _VariableWrap
        _VariableWrap = object
    def __getattribute__(self, l_attribute):
        global _VariableWrap
        if l_attribute in ["VariableByName"]:
            _VariableWrap.__setattr__( VariableName?, VariableValue?)
            return ?
        return _VariableWrap.__getattr__(l_attribute)

Variable = VariableWrap(Variable)

Thanks in advance for any help

Answer 1

Your notation V['key'] is handled by __getitem__ and __setitem__, also, instead of having a global variable is better to hold a reference of the object by instance, so that you can use the same wrapper to wrap different objects.

class VariableWrap():
    def __init__(self, variables):
        self._variables = variables
    def __getitem__(self, l_attribute):
        if l_attribute in ["VariableByName"]:
            return getattr(self._variables,l_attribute)
    def __setitem__(self, l_attribute, value):
        if l_attribute in ["VariableByName"]:
            setattr(self._variables, l_attribute, value)

# The real object where the variables will be stored            
class Object(object):
    VariableByName = 'default'
variables = Object()
wrap = VariableWrap(variables)

# Get directly
assert(variables.VariableByName == 'default')
# Get by the wrapper
assert(wrap['VariableByName'] == 'default')

# Modify object directly and have it reflected in the wrapper
variables.VariableByName = 1
assert(variables.VariableByName == 1) 
assert(wrap['VariableByName'] == 1)

# Modify by the wrapper and have it reflected in the wrapped object
wrap['VariableByName'] = 2
assert(variables.VariableByName == 2) 
assert(wrap['VariableByName'] == 2)