Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Python Python Basics (2015) Letter Game App Random Item

brandonlind2
brandonlind2
7,823 Points
Posted by brandonlind2
brandonlind2
7,823 Points

I dont understand the reason for the -1

Can someone explain why I'm supposed to minus one when create a random index value?

import random
# EXAMPLE
# random_item("Treehouse")
# The randomly selected number is 4.
# The return value would be "h"
def random_item(iterable):
    randomIndex= random.randint(0, len(iterable))-1
    item=iterable[randomIndex]
    return item
Nick Osborne
Nick Osborne
4,612 Points
Nick Osborne
Nick Osborne
4,612 Points

The randomIndex should be: randomIndex = random.randint(0, len(iterable)-1) There is a chance your randomIndex could be -1. You could put randomIndex = random.randInt(1, len(iterable))-1 instead.

evgenypanov
evgenypanov
1,521 Points

Because in some cases you will have IndexError. For example word 'Treehouse' has nine letters. Our range starts from 0 and if we have range 0-9, we have 10 items. And if we try get iterable[10], we've got IndexError, because we have only 9 items in iterable.