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 length:
>>> last = fruit[length-1]>>> print lasta
Alternatively, you can use negative indices, which count backward from the end of the string. The expression fruit[-1] yields th e last letter, fruit[-2] yields the second to last, and so on.