Length¶

The len function, when applied to a string, returns the number of characters in a string.

fruit = "Banana"
print(len(fruit))

(chp08_len1)

To get the last letter of a string, you might be tempted to try something like this:

fruit = "Banana"
sz = len(fruit)
last = fruit[sz]       # ERROR!
print(last)

(chp08_len2)

That won’t work. It causes the runtime error IndexError: string index out of range. The reason is that there is no letter at index position 6 in "Banana". Since we started counting at zero, the six indexes are numbered 0 to 5. To get the last character, we have to subtract 1 from length. Give it a try in the example above.

fruit = "Banana"
sz = len(fruit)
lastch = fruit[sz-1]
print(lastch)

(ch08_len3)

Typically, a Python programmer will access the last character by combining the two lines of code from above.

lastch = fruit[len(fruit)-1]

Check your understanding

strings-6-1: What is printed by the following statements?

s = "python rocks"
print(len(s))

strings-6-2: What is printed by the following statements?

s = "python rocks"
print(s[len(s)-5])