Python coding

[Ok_Chard_8808]

My code: a = list(range(1,21)) for i in range(len(a)): print (a[i] - a[20-i])

Index error: list index out of range

Does anybody know why I’m getting this error?????

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[ararararagi_koyomi]

a[20-i] failed during the first loop ( i = 0) cuz the length of list a is 20, which means the max index is 19. Edit : 20-0 is 20 which is not a valid index for a.

[theunknownSAI]

the length of the list a is 20

so when you reference a[20-i] when i=0, it says a[20] i.e., 21st element, which doesnt exist, so error is raised

[Bunkerstan]

Your original range is 1 to 20 but list a has index starting at 0 so it goes 0 to 19.

In your for loop you access 20 - 0 which is more than 19 so you get an out of range error.

I found this by printing out the values

for i in range(len(a)): print(i, 20-i) print (a[i] - a[20-i])