difference between variables inside and outside of __init__()

Question

Is there any difference at all between these classes besides the name?

class WithClass ():
    def __init__(self):
        self.value = \"Bob\"
    def my_fu         


        

Answer 1

In Python, a class comes with member functions (methods), class variables, attributes/instance variables (and probably class methods too):

class Employee:

    # Class Variable
    company = "mycompany.com"

    def __init__(self, first_name, last_name, position):
        # Instance Variables
        self._first_name = first_name
        self._last_name = last_name
        self._position = position

    # Member function
    def get_full_name(self):
        return f"{self._first_name} {self._last_name}"

---

By creating an instance of the object

my_employee = Employee("John", "Wood", "Software Engineer")

we essentially trigger __init__ that is going to initialise the instance variables of the newly created Employee. This means that _first_name, _last_name and _position are explicit parameters of the specific my_employee instance.

Likewise, member functions return information or change the state of a specific instance.

---

Now any variable defined outside the constructor __init__ are considered to be class variables. Those variables are shared amongst all the instances of the class.

john = Employee("John", "Wood", "Software Engineer")
bob = Employee("Bob", "Smith", "DevOps Engineer0")

print(john.get_full_name())
print(bob.get_full_name())
print(john.company)
print(bob.company)

>>> John Wood
>>> Bob Smith
>>> mycompany.com
>>> mycompany.com

You can also use class methods in order to change the class variable for all the instances of the class. For example:

@classmethod
def change_my_companys_name(cls, name):
    cls.company = name

and now change_my_companys_name()

bob.change_my_companys_name("mynewcompany.com")

will have effect on all the instances of class Employee:

print(bob.company)
print(john.company)

>>> mynewcompany.com
>>> mynewcompany.com