Lists

List stores multiple values.

Initialization

There are couple of ways to initialize list:

Empty list

list_name = []

Initial values

colors = ["red", "green", "blue"]

In this example a list with 3 elements is created.

Size

Size is the count of elements in list.

It's accessed via the len function.

prices = [15, 20, 30] print(len(prices))

Output:

3

Accessing values

List's values can be accessed via indexes starting from 0.

If we declare the following list:

scores = [60, 78, 95, 88]

It's elements are:

So if we type the following line:

print(scores[0], scores[1])

It will print:

60 78

Index out of Bounds

Accessing index outside of the list results in IndexError.

Let's have a list with 4 elements. If we access the 4th or higher index an exception will be thrown.

Such example is:

scores = [60, 78, 95, 88] print(scores[4])

Printing All Elements

Let's have an example in which all elements of list are printed.

scores = [60, 78, 95, 88] count = len(scores) for i in range(0, count): print(scores[i])

Output:

60 78 95 88

Other way to do it is via for in.

scores = [60, 78, 95, 88] for s in scores: print(s)

Inserting Elements

Elements can be inserted using the append function.

Let's have a program which fills list with values:

ages = [] ages.append(15) ages.append(25) ages.append(28)

Product Of Elements

Let's have a program which calculates the product of all even numbers:

numbers = [2, 3, 4, 5] multiplication = 1 for num in numbers: if num % 2 == 0: multiplication *= num print(multiplication)

Output:

8

The only even numbers in the list are 2 and 4 which are multiplied.