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
Functions with return statement¶
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 functions¶
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 >>> math.sqrt(4.0) # Note: need to include the module name in the function call 2 >>> import random >>> random.randint(0, 100) >>> 20
The Anonymous functions¶
The lambda keyword can be used to create small anonymous functions. An example of using lambda keyword is shown below:
>>> total = lambda num1, num2: num1 + num2 #LHS of colon : arguments, # RHS of colon: function body >>> total(1,2) 3
Ready for some practice? Test your understanding at PySchools: Functions.