One of the most powerful features of a programming language is the ability to manipulate variables. A variable is a name that refers to a value.
An assignment statement creates new variables and gives them values:
>>> message = 'And now for something completely different'>>> n = 17>>> pi = 3.1415926535897932
This example makes three assignments. The ﬁrst assigns a string to a new variable named message; the second gives the integer 17 to n; the third assigns the (approximate) value of πto pi.
A common way to represent variables on paper is to write the name with an arrow pointing to the variable’s value. This kind of ﬁgure is called a state diagram because it shows what state each of the variables is in (think of it as the variable’s state of mind). Figure 2.1 shows the result of the previous example.
The type of a variable is the type of the value it refers to.
>>> type(message)<type 'str'>>>> type(n)<type 'int'>>>> type(pi)<type 'float'>