How do I convert string to object type without using eval() in for loop?

Question

class Testclass:

def change(self, obj):
    if(self.ball):
        self.ball=False
        obj.ball=True

main():

A=Testclass()
B=Testclass()
seq=["AB", "BA", "AB"]
for val in seq:
    obj1, obj2=list(val)    #to split "AB" into A, B
    eval(obj1).change(eval(obj2))

.change() method changes object's boolean value to the other object's value. Just for the test.

How can I avoid using eval in this loop? Without eval(), following error appears: 'str' object has no attribute 'change'

I'm using python 3.10

Answer 1

One option would be to use tuples instead of strings:

A = Testclass()
B = Testclass()
seq=[(A, B), (B, A), (A, B)]
for val in seq:
    obj1, obj2=list(val)    #to split "AB" into A, B
    obj1.change(obj2)

Or, combining the unpacking directly with the for loop:

A = Testclass()
B = Testclass()
seq=[(A, B), (B, A), (A, B)]
for obj1, obj2 in seq:
    obj1.change(obj2)

Generally speaking, you'd only use strings if you need to write and read the data to and from a file (or a database or some other external system) or for display on the screen; while it's inside the program, keep things as objects (or numbers etc), don't convert back and forth.