confusion because i can't figure out what is changing the attribute of the object of a class in python

Question

Here is my code
`

class Cats:
    def __init__(self,name):
        self.name=name
        #print(self.name,name,"hello")
    def change_name(self,new_name):
        self.name=new_name
        return 0
        #print(new_name)

cat1=Cats("lion")
print(cat1)
print(cat1.name)


cat2=cat1.change_name("tiger")
print(cat1.name)
print(cat1)
print(cat2)

** Here is the output with my comments/opinion on the side (pls correct me if i am wrong):
**
<__main__.Cats object at 0x7f84272d7640> error because I tried to print the object cat1

lion seems fine coz i printed the attribute of the object and since the name given while initialising was lion, it printed lion

tiger THIS IS WHAT I DON’T UNDERSTAND. why is this output tiger and not lion. what exactly caused this change? Bcoz when I do <<cat2=cat1.change_name("tiger") , it should just assign the value 0 to cat2 but why did it change the value in cat1 ?

<__main__.Cats object at 0x7f84272d7640> error bcoz i tried to print a class

0 seems fine coz chane_name function returns 0 which is assigned to cat2

I was expecting the value of cat1.name to remain the same (it should have remained lion and not changed to tiger)

Asked By: Vikrant KALKAL

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Source

Answer 1

When you call cat1.change_name("tiger"), a few things happen:

The name self is bound to the same object as cat1.
As a result, cat1.name is changed from "lion" to "tiger"
change_name returns 0, not a new instance of Cats.

After this call, cat1.name evaluates to "tiger", not "lion", because the value has changed.

print(cat1) outputs your "error message" because print implicitly calls str on its argument, and since Cats does not define __str__, object.__str__ is used instead, and that produces the string you see.

print(cat2) output 0 because that’s the value that was assigned to cat2 as the return value of cat1.change_name("tiger").

Answered By: chepner

confusion because i can't figure out what is changing the attribute of the object of a class in python

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