Python has various "types" of numbers (numeric literals). We'll mainly focus on integers and floating point numbers.
Integers are just whole numbers, positive or negative. For example: 2 and -2 are examples of integers.
Floating point numbers in Python are notable because they have a decimal point in them, or use an exponential (e) to define the number. For example 2.0 and -2.1 are examples of floating point numbers. 4E2 (4 times 10 to the power of 2) is also an example of a floating point number in Python.
Throughout this course we will be mainly working with integers or simple float number types.
Here is a table of the two main types we will spend most of our time working with some examples:
Examples | Number "Type" |
---|---|
1,2,-5,1000 | Integers |
1.2,-0.5,2e2,3E2 | Floating-point numbers |
Now let's start with some basic arithmetic.
# Addition
2+1
3
# Subtraction
2-1
1
# Multiplication
2*2
4
# Division
3/2
1.5
# Powers
2**3
8
# Can also do roots this way
4**0.5
2.0
# Order of Operations followed in Python
2 + 10 * 10 + 3
105
# Can use parenthesis to specify orders
(2+10) * (10+3)
156
Now that we've seen how to use numbers in Python as a calculator let's see how we can assign names and create variables.
We use a single equals sign to assign labels to variables. Let's see a few examples of how we can do this.
# Let's create an object called "a" and assign it the number 5
a = 5
Now if I call a in my Python script, Python will treat it as the number 5.
# Adding the objects
a+a
10
What happens on reassignment? Will Python let us write it over?
# Reassignment
a = 10
# Check
a
10
Yes! Python allows you to write over assigned variable names. We can also use the variables themselves when doing the reassignment. Here is an example of what I mean:
# Check
a
10
# Use A to redefine A
a = a + a
# Check
a
20
The names you use when creating these labels need to follow a few rules:
1. Names can not start with a number.
2. There can be no spaces in the name, use _ instead.
3. Can't use any of these symbols :'",<>/?|\()!@#$%^&*~-+
3. It's considered best practice (PEP8) that the names are lowercase.
Using variable names can be a very useful way to keep track of different variables in Python. For example:
# Use object names to keep better track of what's going on in your code!
my_income = 100
tax_rate = 0.1
my_taxes = my_income*tax_rate
# Show my taxes!
my_taxes
10.0
So what have we learned? We learned some of the basics of numbers in Python. We also learned how to do arithmetic and use Python as a basic calculator. We then wrapped it up with learning about Variable Assignment in Python.
Up next we'll learn about Strings!