Loops, and where your data lives
INPUT · Slides
01 / 06
You want to remember three fruits. With what you have so far, that means three variables.
What about thirty? Or three hundred? Every extra value costs you another line. No real app gets built that way.
fruit1 = "apple"fruit2 = "orange"fruit3 = "grape"print(fruit1)Result
apple
02 / 06
A list — a container that holds values in order — brings you down to one name however many there are.
You write it by putting the values inside square brackets [ ], separated by commas. Drop that into a variable and the whole lot answers to a single name.
fruits = ["apple", "orange", "grape"]print(fruits)Result
['apple', 'orange', 'grape']
03 / 06
Text is not the only thing a list holds. Numbers work the same.
The usual practice is to put things of one kind in one list — a list of scores, a list of prices, a list of names. Keep to that and working on them together stays easy.
scores = [80, 95, 60]print(scores)Result
[80, 95, 60]
04 / 06
Write [] and you get a list with nothing in it.
It is common to set one up empty first, as the container you are about to fill. Filling it comes a little after the next lesson, so for now just look at the shape.
fruits = []print(fruits)Result
[]
05 / 06
Here is the satisfying part. A list goes straight into a for.
Write for fruit in fruits: and the contents arrive in fruit in order from the front. Three items or three hundred, the code stays the same three lines.
fruits = ["apple", "orange", "grape"]for fruit in fruits: print(fruit)Result
apple orange grape
06 / 06
A list holds things together; for takes them out one at a time. Treat the two as a pair.
fruits = ["apple", "orange"]print(fruits)for fruit in fruits:Next you learn how to ask for just the third one. Name a number and you can grab one without looping over everything.