Understand Constructors in Python Classes

Singleton.py

class Singleton_Student(object):
    _instance = None

    def __new__(cls, *args, **kwargs):
        print("Running __new__() method.")
        if not Singleton_Student._instance:
            Singleton_Student._instance = object.__new__(cls)
        return Singleton_Student._instance

    def __init__(self, first_name, last_name):
        print("Running __init__() method.")
        self.first_name = first_name
        self.last_name = last_name

s1 = Singleton_Student("Yang", "Zhou")
s2 = Singleton_Student("Elon", "Musk")

print(s1)
print(s2)
print(s1 == s2)
print(s1.last_name)
print(s2.last_name)

# Running __new__() method.
# Running __init__() method.
# Running __new__() method.
# Running __init__() method.
# <__main__.Singleton_Student object at 0x7ff1e5a53198>
# <__main__.Singleton_Student object at 0x7ff1e5a53198>
# True
# Musk
# Musk