Variables, assignment, and types

This may seem elementary, but let us review how to define variables and go over the various primitive types in Python.

Defining a variable

Enter the following statement at the Python command prompt >>> to define the variable pi

pi = 3.1415

Note that you do not need to use let, var, or provide any type keywords before a variable declaration. You also don't need to terminate a statement with a semicolon, as you do in many other languages.

defining a variable from an expression

The right side of a variable assignment does not need to be a static value. It can be an expression

a = 1 + 1

Python will evaluate the right side of the assignment operator = and send the result to the left. This property allows you to use an existing variable to redefine itself

a = a + 1

Primitive types

Python includes several primitive data types such as integers int, decimals float, strings str, booleans bool, and null None

a = 1                               # int
b = 3.14                            # float
c = "I'm a double quoted string"    # str
d = 'I\'m a single quoted string'   # str
e = True                            # bool
f = False                           # bool
g = None                            # None

Should I define strings use single or double quotes

Using single or double quotes is mostly a stylistic choice. However, if you intend to use a single quote within a single-quoted string, or a double quote within a double-quoted string, you'll need to escape the embedded quote with a backslash \ character as shown above.

Checking types

You can check the type of a variable or its class by passing it to the built-in type() function.

type(a)