🔒 for loops

[clever niche]

need help understanding this course like idk what those numbers in parenthesis mean

[weak fern]

@clever niche

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[tacit sequoia]

a range is, as advertised, a "range" of numbers. for example, the range of numbers from 1 to 10 is range(1, 11). The reason we write 1, 11 instead of 1, 10 in this case is because the second number is "exclusive." In other words, a range of range(a, b) has all numbers from a to b "except" b. So a range(1, 3) contains 1 and 2.

normally you see ranges with just one number, ie range(5). This just means the starting number is 0

in the case where you see 3 numbers, like range(a, b, c), it still means a range from a to b, but we instead "count by c".

to explain, a range(0, 11, 5) contains 0, 5 and 10

[clever niche]

o so range(2, 5) would be 2 3 4

[tacit sequoia]

yes

[clever niche]

ok and the letter i in that code is just a variable?

[tacit sequoia]

yes, thats what we call the iterator variable

[clever niche]

wat if it was 0, 10, 5)

[tacit sequoia]

its defined in the for loop and represents the current thing you are looping over

if you do for i in x, on the first loop, i is the first element of x. in the second loop, its the second element. and so on

it doesnt to be i either, it can be anything. for exampls for element in x

and then your variable would be called "element"

[clever niche]

ohhh ok

[tacit sequoia]

!e

for i in range(0, 10, 5):
    print(i)

[weak fern]

:white_check_mark: Your 3.12 eval job has completed with return code 0.

001 | 0
002 | 5

[tacit sequoia]

10 doesnt show up because its exclusive

[clever niche]

okkk wow thanks alot

[tacit sequoia]

np

[native hawk]

To elaborate on Karma's "exclusive remark and demo", Python ranges are half open - includes the start, excludes the end. Also with indexing.

>>> s = 'abcdef'
>>> s[0:3]
'abc'
>>> s[3:6]
'def'

See that end end index of the first substring is the start index of the second substring? Using half open ranges lets us do this. If ranges included the end we'd be in a world of pain doing +1 and -1 kind of things at the boundary.

[earnest valve]

!d slice.stop btw

[weak fern]

slice.stop

[earnest valve]

er...

not a very helpful modal

!d range.stop

[weak fern]

range.stop

The value of the stop parameter

[earnest valve]

that's a bit better, but not much. It's "start, stop, step"

[weak fern]

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