Hi guys,
If I want to select a character from the string: fruit = “watermelon” using the code: fruit[len(fruit) - 2] why would it select “o” and not “l”?
Because counting starts at 0 in programming.
W a t e r m e l o n
0 1 2 3 4 5 6 7 8 9
len(fruit) returns 10, 10-2 = 8 so you get the value at the 8th index which is ‘o’.
2 Likes
Consider the entire set of indices for the word watermelon…
-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 # negative indices
| | | | | | | | | |
w a t e r m e l o n
| | | | | | | | | |
0 1 2 3 4 5 6 7 8 9 # positive indices
Since we cannot have two elements with index 0, counting from right to left begins with -1.
Note also that len(string) is redundant given we may use the values directly…
string[len(string) - 2]
is the equivalent of,
string[-2]
once we do the math. If we know we want the second from the end, we can use the literal, without doing any computation.