枚举“列表索引超出范围”的问题

Question

I have a chunk of code that basically goes like this:

x = [6237,5342,9991,6237,1021]
y = [0,0,0,0,0]
for i in x:
  index = x.index(i)
  actualindex = [i for i, n in enumerate(x) if n == i][y[index]]

apparently there is an error on the fifth line where "list index out of range" the first time that i = 6237 .

I changed n == i into n == 6237 and everything worked, but when I changed it back to n == i it stopped working again and returned the same error as before.

Answer 1

You are trying to access an element from an empty list.

This code:

x = [6237,5342,9991,6237,1021]
my_list = [i for i, n in enumerate(x) if n == i]

always returns an empty list, since the number of elements in x is only 5 i can only ever be equal to {0,1,2,3,4} therefore i can never equal any of the elements in x since all of them are greater than 4.

print(len(my_list)) # 0
my_list[0]

gives "list index out of range" because any index you give to the list will be out of range since its length is zero (its an empty list).