02 variables
title: Python Variables author: Juma Shafara date: "2023-11" date-modified: "2024-08-14" description: What are variables and how do we use them in Python? keywords: [python, python programming, python variables]¶
- Varibles are used to store values.
- To create a variable, use the equal sign `(=)`.
In the examples below, we create varibales name fruit and name and we assign them values 'mango' and 'viola' respectively
fruit = 'mango'
name = 'voila'
# printing out
print(name, ' likes ', fruit )
voila likes mango
Rules to consider¶
Before choosing a variable name, consider the following.
- Spaces are not allowed in a variable name eg `my age = 34`
- A variable name can not start with number eg `1name = 'Chris'`
- Variable names can not have special characters eg `n@me = 'Comfort'`
- Are case sensitive. Ie Name and name are not the same!
Examples of good variable names
character = 'Peter Griffin'
my_favorite_character = 'Stewie Griffin' # snake case
myFavoriteCharacter = 'Meg Griffin' # camel case
MyFavoriteCharacter = 'Brian Griffin' # Pascal case
Data Types¶
In this section of the tutorial, you will learn the most basic data types in Python
Numbers¶
These are two basic types of numbers and they are called:
- integer(numbers without decimal places)
- floating point numbers(numbers with decimal places)
# python numbers
# Integers
age = 45
population = 45000000
# Floating point numbers
height = 1.7
weight = 147.45
Strings¶
Strings are simply text. A string must be surrounded by single or double quotes
# Strings
name = 'Juma'
other_name = "Masaba Calvin"
statement = 'I love coding'
Booleans¶
Boolean data type can only have on fo these values: True or False
Note!
The first letter of a Boolean is in upper case.
Booleans are often the result of evaluated expressions.
Forexample, when you compare two numbers, Python evaluates the expression and returns either True or False
print(5 == 5)
print(10 > 5)
print(20 < 10)
True True False
These are often used in if statments.
In this example, if the value of the variable age is more than 18, the program will tell the user that they are allowed to enter
age = 19
if age > 18:
print('You are allowed to enter.')
You are allowed to enter.
Note!
You will learn more about if statements later in the course
Checking the Type of a Boolean¶
We can check the data type of a Boolean variable using the type() method.
married = True
print(type(married))
<class 'bool'>
Lists¶
- A list is an ordered collection of data
- It can contain strings, numbers or even other lists
- Lists are written with square brackets (`[]`)
- The values in lists (also called elements) are separated by commas (`,`)
# Lists
names = ['juma', 'john', 'calvin']
print(names)
['juma', 'john', 'calvin']
A list can contain mixed data types
other_stuff = ['mango', True, 38]
print(other_stuff)
['mango', True, 38]
Checking data types¶
To check the data type of an object in python, use type(object), for example, below we get the data type of the object stored in names
# Which data type
print(type(names))
list
Converting Types¶
Convert to String¶
The str() method returns the string version of a given object
# convert an integer to a string
age = 45
message = 'Peter Griffin is '+ str(age) + ' years old'
print(message)
Peter Griffin is 45 years old
Convert to Integer¶
The int() method returns the integer version of the given object.
# Convert floating point to integer
pi = 3.14159
print(int(pi))
3
Convert to Float¶
The float() method returns the floating point version of the given object.
side = 4
print(float(side))
4.0
Exercise¶
Write a program to assign the number 34.5678 to a variable named “number” then display the number rounded to the nearest integer value.