[Python] Python destructing two objects when (I think) I only destructed one [closed]

I am learning Python and decided to create a simple class to help me understand. The class is for Tennis Balls. I have a class attribute of num_balls, and instance attributes of serial_number and age.

I create two instances of the TennisBall class and name them 'a' and 'b'. When I call the destructor for 'a', instance 'b' also gets destructed.

class TennisBall:
ball_count = 0

def __init__(self, serial_number, age):
self.serial_number = serial_number
self.age = age
print("New Tennis Ball created {}!".format(self.serial_number))
TennisBall.ball_count +=1

def __del__(self):
print("Tennis ball {} has been deleted ".format(self.serial_number))
TennisBall.ball_count -= 1




a = TennisBall(1234, 0)
print("Num balls: {} ".format(TennisBall.ball_count))

b = TennisBall(2345, 0)
print("Num balls: {} ".format(TennisBall.ball_count))

del a
print("Num balls after del ball a: {} ".format(TennisBall.ball_count))


I destructed instance 'a' and it was deleted as expected. However, instance 'b' was also destructed, even though I did not call that.

I tried destructing 'b' instead and again both 'a' and 'b' were destructed.

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