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Engineering LibreTexts

21.2: len

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  • len is a built-in function that returns the number of characters in a string:

    >>> fruit = 'banana'
    >>> len(fruit)

    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 last

    Alternatively, 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.

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