python_class_testing.py

class Person:

    # this is a private class attr
    __private_class_attr = "I am a private class attr"

    # this is a class wide attribute ***********************************
    public_class_wide_attribute = 0

    # this is what allows you to instantiate objects - aka construct them
    # which is why its called a constructor
    def __init__(self):
        # this is an instance attribute *********************************
        self.instance_attribute = 0
        # this is a private instance attribute ****************************
        # the 'dunder' or double underscore at the beginning is what makes it private
        self.__private_instance_attr = "I am a private instance attr"

    # this is what allows us to grab the private instance attr
    def get_private_instance_attr(self):
        return self.__private_instance_attr

    # this is what allow us to grab the private class attr, which can be static since it does not rely on any instance
    @staticmethod
    def get_private_class_attr():
        return Person.__private_class_attr


# instantiate objects
nick = Person()
matt = Person()

# cant access private attr publicly unless you create a way to do so from within the class
#print(nick.__private_instance_attr)  # *** REMOVE THE # AT THE FRONT OF THIS LINE TO SEE ERROR *****

# here is how you access private instance attr, publicly
print(nick.get_private_instance_attr())
print()

# here is how you access private class attr, from either an instance or statically from the class
print(nick.get_private_class_attr())  # access from an instance
print(Person.get_private_class_attr())  # access from class
print()

# show class attr on both instantiated objects (Person)
print(f'should be "0":')
print(f'class attr: nick: {nick.public_class_wide_attribute} is the same as matt: {matt.public_class_wide_attribute}')
print()

# change public class attr on nick, also changes on matt
Person.public_class_wide_attribute = 99
print(f'both should be 99, this attribute belongs to the class Person, not each instance')
print(f'should be 99: nick: {nick.public_class_wide_attribute} is the same as matt: {matt.public_class_wide_attribute}')
print()

# instance attributes
print(f'original instance attributes will be the same: nick:{nick.instance_attribute} matt:{matt.instance_attribute}')
# change instance attribute
matt.instance_attribute = 150
nick.instance_attribute = 300
print(f'instance attributes now different: nick: {nick.instance_attribute} matt: {matt.instance_attribute}')

# OUTPUT:
"""
I am a private instance attr

I am a private class attr
I am a private class attr

should be "0":
class attr: nick: 0 is the same as matt: 0

both should be 99, this attribute belongs to the class Person, not each instance
should be 99: nick: 99 is the same as matt: 99

original instance attributes will be the same: nick:0 matt:0
instance attributes now different: nick: 300 matt: 150

Process finished with exit code 0
"""