In an expression, arithmetic operations are normally performed in the following order:

• Exponentiation is always performed first.
• Multiplication, division and modulo arithmetic are performed next.
• Addition and subtraction are performed last.

You can use () characters, known as parentheses, to force arithmetic operations to be performed in an a particular order in an expression. Operations inside parentheses are always performed first. For example:

x = 3
y = 13
z = 7
result = x * (y - z)
print result   # the result displayed is 18, not 32, as (y - z) is done first

If parentheses are contained inside one another in an expression, the operations in inner parentheses are performed first:

x = 3
y = 13
z = 7
result = x * (y - (z * 2))  # result is now -3