9.6. Length¶

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

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

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.

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))

• (A) 11
• The blank counts as a character.
• (B) 12
• Yes, there are 12 characters in the string.

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

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

• (A) o
• Take a look at the index calculation again, len(s)-5.
• (B) r
• Yes, len(s) is 12 and 12-5 is 7. Use 7 as index and remember to start counting with 0.
• (C) s
• s is at index 11
• (D) Error, len(s) is 12 and there is no index 12.
• You subtract 5 before using the index operator so it will work.