Functions

A function is a set of statements that perform a specific task. Using functions helps in breaking our program into smaller parts. Programs will be more organized if we use functions as it avoids repetition and makes code reusable. Look at the following syntax:

def function_name(parameters):
    statement(s)

Refer to the following example:

def welcome(name):
    print("Hello " + name + ", Welcome to Python Programming !")

welcome("John")

Output:
Hello John, Welcome to Python Programming !

The return statement

The return statement is used to exit a function. Refer to the following syntax:

return [expression_list]

This statement may contain an expression where a value has to be returned. If there is no expression, then the function will return a None object, as shown in the following example:

def return_value(a):
    if a >= 0:
        return a
    else:
        return -a
print(return_value(2))
print(return_value(-4))

Output:
2
4

Lambda functions

In Python, an anonymous function is a function that is defined without a name and is called a lambda function, as it is defined using a keyword lambda. We use these functions whenever we require a function for a short period of time.

Lambda functions are used along with built-in functions, such as filter(), and map().

The filter() function returns a list of elements and has only one iterable as input. The following shows an example using filter():

numbers = [10, 25, 54, 86, 89, 11, 33, 22]
new_numbers = list(filter(lambda x: (x%2 == 0) , numbers))
print(new_numbers)

Output:
[10, 54, 86, 22]

In this example, the filter() function is taking a lambda function and a list as an argument.

The map() function returns a list of results after applying the specified function. Now, let's look at an example using map():

my_list = [1, 5, 4, 6, 8, 11, 3, 12]
new_list = list(map(lambda x: x * 2 , my_list))
print(new_list)

Output:
[2, 10, 8, 12, 16, 22, 6, 24]

Here, the map() function is taking a lambda function and a list.