What is function?

• Function is way of problem solving by dividing the problem into sub-problems and finding their individual solution and combining them to solve original problem.

Function Definition:

• defining the role of function
• actions to be performed by functions are written in the form of statements here.

syntax:

    def function_name(parameters_seperated_by_commas):
        statements

notice the : and indentation i.e four white spaces.

Some Rules:

• function_name must not be python keyword
• code following colon(:) must be indented.

Function Call:

• calling the defined function

• to execute the work we need to call the defined function.
  to execute function, We need to invoke function.

   function_name(arguments_seperated_by_commas)
  

Suppose we want to write a program that draws a house, a car and a cat.
Without use of function we end up writing whole code for drawing house, a car and a cat at a place.

     def main():
         statements for drawing house
         statements for drawing car
         statements for drawing cat

which works fine but tracking, debugging is difficult and probably not the best practice.
so what we do here is make function for individual work like:

     def draw_house():
         statements

     def draw_car():
         statements

     def draw_cat():
         statements

and we will call the defined function in our main function as:

     def main():

         draw_house()

         draw_car()

         draw_cat()

         print("task completed")

Types of Functions:

• Void Functions:

  • The function that doesn't return anything.

  • simply speaking, The return type is None
    for example:
    If we want to add two numbers given to function and print it's result then:

    def addition(num1,num2):
        print(f"{num1}+{num2}=",num1+num2)
    

• Fruitful Functions:

  • The function that returns some value

  • The return type is not null.
    for example:

    def addition(num1,num2):
        return num1+num2
    

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