The following are examples of variables in Python:

x
U2
patient_name
VaRiAbLe
RESULT2
_LabName

A variable can be any collection of letters, digits and underscore (_) characters, except that the first character cannot be a digit. Also, you cannot use a reserved word as a variable: a reserved word is anything that has a predefined meaning in Python. (Examples of reserved words include if and else, which are discussed in Conditional Statements and Loops.)

	The limitation on what a variable can be makes it easy to distinguish between numbers, strings and variables: Anything that starts with a digit (or a negative sign or decimal point) is a number; Anything that starts with a quote character is a string; Anything else that is not a reserved word is a variable. It's a little more complicated than that in reality, but this is a good working rule.

Note that variables in Python are case sensitive. This means that it matters whether you use capital letters or not. For example, the following variables are all different:

labname
LABNAME
LabName