Operators in Python

Arithmetic operators

• Some operators in Python will look familiar (+, -, *, /)• Others are new to you (%, //, **)• All of these do work with numbers and produce numbers

For any operator you need to know

• These are questions you should ask every time you see a new operator – not just arithmetical but any operator!• How many arguments does it have and what do they mean• What data type are the arguments? (int, float, string, etc.)• The semantics of the operator, which is what does it do? What does

it mean?• What data type does the operator return? NOT always the same as

the type of the arguments• What is its precedence or priority with other operators?

Example: addition +

• It has two arguments (we are talking about the addition operator here, not the unary plus sign)• The arguments can be ints or floats• It produces the sum of the values of the two arguments• It produces an integer if the arguments are both integers, otherwise it

produces a floating point number• It is relatively low precedence, comes after * and /

Other familiar operators

• Multiplication * works on ints and floats, produces an int if 2 int arguments, float otherwise• Subtraction works similarly to multiplication• Division / works on ints and floats, but always returns a float• Precedence is as in algebra, multiplication and division higher than

addition and subtraction• If there are two operators in an expression of the same level of

precedence, they are executed left to right in the expression• a + b + c is done as (a + b) + c

New Operators // and %

• // is similar to division but always gives the whole number part of the quotient (result of dividing)• If give two ints, will give an int, otherwise a float• 5 // 4 = 1, 5 // 4.0 = 1.0 (not 1.25)

• % is the modulus operator, gives the remainder of a division operation• If give two ints, yields an int, otherwise a float• 13 % 4 = 1 (the remainder when 13 is divided by 4), 8 % 4 = 0

• These two operators have the same precedence as multiplication and division

New Operator **

• ** means exponentiation• Has two arguments a ** b• a is the base, b is the power to raise a to• 5 **3 = 5 * 5 * 5, 7 ** 2 = 7 * 7 = 49• The precedence is higher than the other arithmetic operators• The base or power can be integer or float• As usual, if two int arguments, gives int result, otherwise float• Is right associative (different from all of the other operators)• 4 ** 3 ** 2 = 4 ** (3 ** 2) = 4 ** 9 = 262144