Classes and Functions

April 23, 2019  

The basic purpose of classes and functions is to group together pieces of related code. The major difference between the two is that a function does something whereas a class is something.

For example, if person was a class, walk() and eat() would be functions.

Both classes and functions can contain other functions. If a function is inside another function, it’s called a sub-function. If a function is included inside a class, it’s called a method. Subclasses also exist, but they are created by a process called inheritance.

Let’s define a function using the def statement:

def function_name([parameter list]):
    # rest of function

To define a class in python, you use the class statement:

class Someclass([argument list]):
    # class constructor
    __init__():
        # Constructor code
    # class methods
    def ...

You create subclasses that contain all the attributes and methods of another class using inheritance. Inheritance is an important concept in object-oriented programming. Inheritance helps prevent repetition in code, and it allows programmers to build complex programs from simpler building blocks.

To create a class that inherits from another class, you refer to the parent when defining the class:

class ChildClass(ParentClass):

This is easier to understand with an example–check out this form class:

class ContactForm(forms.Form):
    subject = forms.CharField(max_length=100)
    email = forms.EmailField(required=False)
    message = forms.CharField(widget=forms.Textarea)

In this example, the class inherits from Django’s forms.Form class, which make all of the methods and attributes of the parent class (forms.Form) available in the child class (subclass) ContactForm.

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