Function

Function Declaration

Function is commonly used to group a series of statements together to achieve a specific objective.

To declare a function:

							
def add_one(x):
    '''
    This function takes in a number as argument and increment the number by 1
    '''
    print x + 1     	
						

To invoke a function:

							
>>> add_one(5)
6
>>> add_one(2)
3
						

Fruitful Function

By default, all functions return None. Function that returns value is known as fruitful function.

def add_one(x):
    '''
    This function takes in a number as argument and increment the number by 1
    '''
    return x + 1
						

It is a good practice to assign the value returned by a function to a variable.

>>> x = add_one(5)
>>> print x
6
						

Using Built-in Function

The python installation is pre-packaged with many modules which contain some commonly used functions. One such module is the math module. To use a builtin module, you have to use the import statement.

>>> import math
# Note: need to include the module name in the function call
>>> math.sqrt(4.0)              
2
>>> import random
>>> random.randint(0, 100)
>>> 20
						

Anonymous Function

The lambda keyword can be used to create small anonymous functions. An example of using lambda keyword is shown below:

							
# LHS of colon : arguments 
# RHS of colon: function body
>>> total = lambda num1, num2: num1 + num2      
>>> total(1,2)
3
						

Code Snippets

This section will contain some code snippets to show some practical use of the topic that you have learnt.

# Calculation without using function
# ----------------------------------
# circle with radius of 3
areaOfCircle1 = 3.14 * 3 * 3

# circle with radius of 4
areaOfCircle2 = 3.14 * 4 * 4

totalArea = areaOfCircle1 + areaOfCircle2


# Calculation using function
# ----------------------------------
def areaOfCircle(r):
	return 3.14 * r * r

totalArea = areaOfCircle(3) + areaOfCircle(4)