Programming Fundamentals › Programming Basics

Operator Precedence

The rules for which operators bind first in an expression.

Also known as: order of operations, operator priority, precedence rules

Operator precedence decides which operators apply first in an expression without parentheses, like the school rule that multiplication comes before addition.

2 + 3 * 4        # 14, not 20: * binds tighter than +
(2 + 3) * 4      # 20

A rough order, highest first

1. Parentheses and calls
2. Exponent (**)
3. Unary -, not, !
4. * / %
5. + -
6. Comparisons (< == >=)
7. and / &&
8. or / ||
9. Assignment

The exact table differs between languages, so check yours.

Where it bites

if a or b and c:         # means: a or (b and c)
if not x == y:           # Python: not (x == y)

and binds tighter than or, so mixing them without brackets is a classic source of wrong conditions. In JavaScript, && over || behaves the same way, and ?? can’t be mixed with them without parentheses.

const label = "Total: " + 2 + 3;     // "Total: 23", not "Total: 5"

Evaluation goes left to right for operators of equal precedence (mostly), so string concatenation happens before the second +.

The practical rule

You don’t need to memorize the table. Add parentheses whenever readers might have to think about it. (a and b) or c costs nothing and removes doubt. If an expression needs a precedence table to understand, split it into named steps (readability).