How to change object variables in for loop in python

Question

I'm not sure, whether it's an easy problem with easy solution or it's something that needs to dig a little deeper.

Let's say I have an object Item with variables Item.a and Item.b. Now I have two instances of these objects: Item1 and Item2

What I need is something like this:

for (value_1, value_2) in [(Item1.a, Item2.a), (Item1.b, Item2.b)]:
    if value_1 != value_2:
        value_1 = value_2

Of course this one is only an example of more complex problem. The substitution is ok, it finds differences between objects and substitutes them. The problem is, that all the time I'm doing it on copies of those variables, not on object references. As soon as it finish the loop, I can print both Item1 and Item2 and they are the same as before loop.

Is there any possibility to pass references into a loop? I know how to do it with lists, but I could not find an answer to objects.

Answer 1

Well, [(Item1.a, Item2.a), (Item1.b, Item2.b)] just creates a list of tuples of some values. Already by creating this you loose the connection to ItemX. Your problem is not related to the loop.

Maybe you want

for prop in ('a', 'b'):
    i2prop = getattr(Item2, prop)
    if getattr(Item1, prop) != i2prop:
        setattr(Item1, prop, i2prop)

Or something similar but with passing ItemX to the loop too:

for x, y, prop in ((Item1, Item2, 'a'), (Item1, Item2, 'b')):
    yprop = getattr(y, prop)
    if getattr(x, prop) != yprop:
        setattr(x, prop, yprop)