Why KeyError: 0

keyerror, python, python-3.x

Solution

You insert `0` for `i = 1` here:

sumsdivs = {}
for i in range(1, 10000):
    tmpls = []
    for j in range(1, i):
        if i % j == 0:
            tmpls.append(j)
    sumsdivs[i] = sum(tmpls)

The inner loop never runs (`range(1, 1)` is empty), and `sum([])` is 0.

Demo:

>>> sumsdivs = {}
>>> for i in range(1, 2):
...     tmpls = []
...     for j in range(1, i):
...         if i % j == 0:
...             tmpls.append(j)
...     sumsdivs[i] = sum(tmpls)
... 
>>> sumsdivs
{1: 0}
>>> sum([])
0

So `sumsdivs[1]` is 0, and `sumsdivs[sumsdivs[0]]` throws a `KeyError`:

>>> sumsdivs[sumsdivs[1]]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 0

Problem

I'm attempting to solve Project Euler 21 but I'm getting KeyError: 0 which normally occurs when you refer to a dictionary key that doesn't exist. However, I thought I had solved that problem with the < 10000 condition. The error refers to the first 'if' statement in the main() function. ``` sumsdivs = {} for i in range(1, 10000): tmpls = [] for j in range(1, i): if i % j == 0: tmpls.append(j) sumsdivs[i] = sum(tmpls) amls = [] def main(): for i in range(1, 10000): if sumsdivs[i] < 10000 and sumsdivs[i] == sumsdivs[sumsdivs[i]]: if sumsdivs[i] not in amls: amls.append(sumsdivs[i]) if sumsdivs[sumsdivs[i]] not in amls: amls.append(sumsdivs[sumsdivs[i]]) return sum(amls) print(main()) ``` Any ideas?

Original source