Updating values
Changing a variable based on itself is so common that it has shortcuts:
score = 10 score += 5 # same as score = score + 5 -> 15 score -= 3 # 12 score *= 2 # 24 score /= 4 # 6.0
Order of operations is the usual maths order: **, then * / // %, then + -. Brackets go first.
score box: 10, 15, 12, 24, then 6.0 (/= always gives a float).See it run
steps = 10 steps += 5 steps = steps + 5 steps *= 2
Each row of the table is one change to steps. Read the rows top to bottom.
Practice updating values
Exercise 1
Start with balance = 100. Deposit 50 with +=, withdraw 30 with -=, then double it with *=. It should end at 240.
Exercise 2
A game character starts with xp = 0.
- They win 3 battles worth 40 xp each: add it in one line with += and *.
- A trap costs 25 xp (-=).
- A bonus weekend triples what is left (*=).
xp should end at 285.
Exercise 3
This cafe bill in the code editor below has a bug. It should be the food (2 coffees at 3.5, 1 cake at 4.25) plus a 10% tip, so the whole food cost gets multiplied by 1.1.
- Fix the line with brackets so
billis 12.375. - Then split it between 3 friends with
/=(each pays 4.125).
Free lesson: use the editor to practice it.
Practice
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Run your code, then choose Play to follow its execution.