Types of data
1. Choosing between primitive types
2. Declaring variables with initial values

Types of data

Programs represent concepts from a certain problem domain in their own solution domain. When you model elements of the problem you want to solve in your code, you choose types of data.

We use values to represent data and variables to keep track of values.

All values in Python are objects. The type or class of an object determines what values it can take on, what attributes it has, and what functions it is compatible with.

Choosing between primitive types

In Python, you can work with four primitive data types:

Integers for whole numbers such as 1, -20, and 0
Floats for fractional values such as 0.25 and -1.333
Strings for text such as 'I enjoy coding' and 'A'
Booleans for values that are either True or False

The single equal = syntax assigns a value to a variable.

planet = 'Neptune'          # string
orbital_period_years = 165  # integer
mass_ratio_to_earth = 17.15 # float
is_inner_planet = False     # boolean

Declaring variables with initial values

When values are written into a program literally, the syntax determines their type. Putting quotation marks around a value will declare it as a string. Using a floating point (decimal point) will declare a numerical value as a string.

# declaring an initial string value and assigning it to a variable
planet = 'Neptune'

Booleans must be capitalized. Otherwise you will get a NameError because the computer thinks you are referencing a variable named false.

is_inner_planet = false

  File "filename.py>", line 1
NameError: name 'false' is not defined

Note: Only suffering can come from actually naming a variable false.

Other errors in the syntax of declaring a value can also cause NameErrors and SyntaxErrors. But, it is better to have a known error that you can fix than to accidentally use the wrong data type and have to figure out why a program is misbehaving.