Variables, Assignment, and Number Types

A variable is a name that refers to a value so you can use it again later. You create one by giving it a value.

Python is dynamically typed: a variable name can point to a value of any type, and unlike Java or C there is no need to declare the variable first.

A variable name can use letters, digits, and the underscore symbol, but it cannot start with a digit. It is considered best practice to use meaningful names.

In math, = states that two things are equal. In Python it is an assignment: evaluate the expression on the right side, then store that result in the variable on the left.

That is why a line which looks impossible in math is perfectly ordinary in Python.

Every value in Python has a type. These are the three number-like types. Text has its own type, str, which is coming up next.

The most basic numerical type is the integer. Any number written without a decimal point is an integer. Python integers are variable-precision, so you can do computations that would overflow in other languages.

The floating-point type stores fractional numbers. Writing a decimal point is what makes a value a float, even when the value is a whole number: 4.0 is a float, 4 is an int.

The Boolean type is a simple type with two possible values: True and False. Boolean values are case-sensitive, so unlike some other languages, True and False must be capitalized.

Comparison operators produce a Boolean value.