Lists in Python

• Computing
• Lower Secondary (Key Stage 3)

Lists in Python

Cited from W3Schools.com

Said Ahghari

Data Types

Python supports various data types such as integers, floats, strings, boolean, and lists.

Data Types for Variables

In Python, variables can hold different types of data, such as numbers, strings, boolean, and lists. Each data type has its own characteristics and usage.

Lists

In python one of the most used data structures is a list.

Lists are used to store similar data, one item after another.

For example:

• items you need to buy from a shopping list
• names of students in a class

A list is an example of a 1 Dimensional array.

List Data Type

Lists are a collection of items that can be manipulated and accessed individually. The list data type in Python is used to store multiple values in a single variable. It is denoted by square brackets ([]).

marks = [25, 65, 95, 33]    #a list of 4 numbers  

names = []                              #an empty list

Coding Activity: creating and outputting a list

In Python, create a list of 5 students.  Output the list. 

Solution

myStudents = ["Said", "John", "Iman", "Nour", "Jane"]

print(myStudents)

Finding the number of items in a list

To find the number of items in a list use the len() function.

myStudents = ["Said", "John", "Iman", "Nour", "Jane"]

print(len(myStudents))

Output:

5

List items' position

Each list item is held in a position in the list.

The list position starts from zero (0).

0	1	2	3	4
Said	John	Iman	Nour	Jane

Position (index)

List item

Slide 8: Recap and Summary

In this lesson, we learned about various data types in Python, including numeric, string, boolean, list, tuple, and dictionary data types.

How to access individual items in a list?

How to access individual items in a list?

To access the individual items of a list, use the index number.

myStudents = ["Said", "John", "Iman", "Nour", "Jane"]

print(myStudents [1] )

Which item is displayed?

Negative Indexing

Negative indexing means start from the end.

-1 refers to the last item, -2 refers to the second last item etc.

myStudents = ["Said", "John", "Iman", "Nour", "Jane"]

print (myStudents [-2] )

Which item is displayed?

Range of Indexes

You can specify a range of indexes by specifying where to start and where to end the range.

When specifying a range, the return value will not include the the ending range.

myStudents = ["Said", "John", "Iman", "Nour", "Jane"]

print (myStudents [1:4] )

Which items are displayed?

What is the output type?

myStudents = ["Said", "John", "Iman", "Nour", "Jane"]
print (myStudents [1:4] )
Which items are displayed?
What is the output type?

Answers:

['John', 'Iman', 'Nour']

It is a list because of the square brackets ([ ])

How many items will be outputted using the following code?
fruitList = ["apple", "banana", "cherry", "orange", "kiwi", "melon", "mango"]
print(fruitList[ :4])

1. Three items
2. Four items
3. None
4. Five items

Explain the following line of code.
print(fruitList[:4])

What will be the result of the following syntax:
mylist = ['apple', 'banana', 'cherry']
print(mylist[-1])

1. Apple
2. Banana
3. Cherry
4. Error message

What will be the result of the following syntax:
mylist = ['apple', 'banana', 'cherry', 'kiwi', 'melon', 'mango']
print(mylist[-2:])

1. ['kiwi', 'melon', 'mango']
2. ['melon', 'mango']
3. error message
4. ['apple', 'banana']

What is the output of the code below:
my_list = [1, 2, 3, 4, 5]
print(my_list[::-1])

What is the output of the code below:
my_list = [1, 2, 3, 4, 5]
print(my_list[::-1])