len is a built-in function that returns the number of characters in a string:
>>> fruit = 'banana' >>> len(fruit) 6
To get the last letter of a string, you might be tempted to try something like this:
>>> length = len(fruit) >>> last = fruit[length] IndexError: string index out of range
The reason for the
IndexError is that there is no letter in
’banana’ with the index 6. Since we started counting at zero, the six letters are numbered 0 to 5. To get the last character, you have to subtract 1 from
>>> last = fruit[length-1] >>> last 'a'
Or you can use negative indices, which count backward from the end of the string. The expression
fruit[-1] yields the last letter,
fruit[-2] yields the second to last, and so on.