when to use functions in python and when not to?

Functions are a way of compartmentalizing code such that it makes it both easier to read and easier to manage. In this case, there are a few concepts you must understand before implementing functions to solve your problem.

Functions follow the format:

def functionName(): #this defines the function
    print("This is inside the function.") #this is code inside the function

functionName() #this calls the function

A few things to note:

• code that belongs to the function is indented
• in order for the function to execute, it first has to be invoked (i.e. called)

So your function aims to calculate the area of a rectangle using width and height variables. In order for your function to work you would first need to invoke the function itself and then remove the unneeded parameters as you are asking for them as input anyway. This would give you:

def area_rectangle():

    width=int(input("Enter the width of rectangle: "))
    height=int(input("Enter the height of rectangle: "))
    area=width*height
    print (area)

area_rectangle()

Another way to go about this would be to make use of parameters. Parameters are values passed to a function by the line of code that invokes them, and they are given within the parentheses:

def functionName (my_param):
    print (my_param)

fucntionName (my_param)

Using parameters to solve your problem would look something like this:

def area_rectangle(width, height):
    area=width*height
    print (area)


width=int(input("Enter the width of rectangle: "))
height=int(input("Enter the height of rectangle: "))

area_rectangle(width, height)

Another side note is on return values. Rather than printing the result of a function within the function itself, you can return it to the line that invoked it and then make use of it outside the function:

def area_rectangle(width, height):
    area=width*height
    return area


width=int(input("Enter the width of rectangle: "))
height=int(input("Enter the height of rectangle: "))

area = area_rectangle(width, height)

print ("The area is {}".format(area))

Functions are an essential part of Python, and I suggest reading some tutorials on them, as there is many more things you can do with them. Some good ones...

learnpython.org - Functions

tutorialspoint.com - Python Functions

First,

You should indent your code

Second,

Now to get your code working you should call the function area_rectangle()

Corrected Code

def area_rectangle():

   width=int(input("Enter the width of rectangle: "))
   height=int(input("Enter the height of rectangle: "))
   area=width*height
   print area
area_rectangle()

Indentation is the key for Python (there are no {} just indentation)

Refer python documentation

You cant executing your function because

1. You are not invoking (calling) it at the bottom.

   def area_rectangle(width,height):
       width=int(input("Enter the width of rectangle: "))
       height=int(input("Enter the height of rectangle: "))
       area=width*height
       print area
   
   area_rectangle()
   

2. You are passing the required argument "width and height" to the function "area_rectangle" which is meaningless because you are accepting them from the user within the function. just call the function to work.

   Functions are a group of statements which gives you the answer for your problem statement. In your case if you are writing it as a function then you can resuse this value "area_rectangle" anywhere you want. you don't need to write those lines again.