The Four Families

You've met operators one at a time. Here's the full map, in four families:

Arithmetic, + - * / % ** //, produce numbers

Comparison, > < >= <= == !=, produce Booleans

Logical, and or not / && || !, combine Booleans

Assignment, = += -= *= /=, store values

Compound assignment is the family you haven't met. total += 5 is shorthand for total = total + 5. It's shorter, and it's the standard way to accumulate a running total.

Compound assignment

PYTHON

total = 0
total += 10   # same as total = total + 10
total *= 2    # same as total = total * 2

JAVASCRIPT

let total = 0;
// same as total = total + 10
total += 10;
total *= 2;   // same as total = total * 2

Compare → Identical in both languages. You'll use += constantly once loops arrive in Module 12: it's how a running total grows one item at a time.

EXAMPLE

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YOUR TURN

Your turn → This is the accumulator pattern, the backbone of every total, every counter, every sum you'll ever write. Add two more donations.

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Syntax has to be exact. Every quote, bracket and parenthesis needs its partner, and in Python the spaces at the start of a line count. One slip and the program won't run; the message will say where.

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