CODEWITHSUNDEEP
pythonindexing
user5676791
user5676791

Reputation:

Python error list index is out of range

I know this is a rookie question but I keep getting an error I don't usually get. "Index error: List index out of range on line 12." where it says the 2 'nums'. I thought it was perfectly fine to call variables out side of a loop?

lisp = []
new = []

for x in range(1, 11):
    num = int((x * (3*x - 1))/2)
    lisp.append(num)

x = 0
y = 2

for i in lisp[1:]:
    num1 = lisp[x] + i
    num2 = lisp[y] + i
    dif1 = i - lisp[x]
    dif2 = lisp[y] - i
    smallList = [num1, num2, dif1, dif2]
    new.append(smallList)

    x += 1
    y += 1

print(new)

Upvotes: 1

Views: 81

Answers (2)

Andy_Jake
Andy_Jake

Reputation: 144

Check and put conditions on:

x += 1
y += 1

y is going beyond the index on the line:

num2 = lisp[y] + i

Upvotes: 0

glegoux
glegoux

Reputation: 3603

Fix using ipython.

script.py:

lisp = []
new = []

for x in range(1, 11):
    num = int((x * (3*x - 1))/2)
    lisp.append(num)

x = 0
y = 2

for i in lisp[1:]:
    num1 = lisp[x] + i
    num2 = lisp[y] + i
    dif1 = i - lisp[x]
    dif2 = lisp[y] - i
    smallList = [num1, num2, dif1, dif2]
    new.append(smallList)

    x += 1
    y += 1

print(new)

Launch ipython and do:

In [1]: run script.py
     11 for i in lisp[1:]:
     12     num1 = lisp[x] + i
---> 13     num2 = lisp[y] + i
     14     dif1 = i - lisp[x]
     15     dif2 = lisp[y] - i

IndexError: list index out of range

In [2]: y
Out[2]: 10

In [3]: len(lisp)
Out[3]: 10

Here y = 10, but len(lisp) = 10 valid index are between 0 and 9 (both inclusive, 0-based) and 10 is out of this range.

Upvotes: 2

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