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8.9: Lists and Strings

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  • A string is a sequence of characters and a list is a sequence of values, but a list of characters is not the same as a string. To convert from a string to a list of characters, you can use list:

    >>> s = 'spam'
    >>> t = list(s)
    >>> print(t)
    ['s', 'p', 'a', 'm']

    Because list is the name of a built-in function, you should avoid using it as a variable name. I also avoid the letter l because it looks too much like the number 1. So that's why I use t.

    The list function breaks a string into individual letters. If you want to break a string into words, you can use the split method:

    >>> s = 'pining for the fjords'
    >>> t = s.split()
    >>> print(t)
    ['pining', 'for', 'the', 'fjords']
    >>> print(t[2])

    Once you have used split to break the string into a list of words, you can use the index operator (square bracket) to look at a particular word in the list.

    You can call split with an optional argument called a delimiter that specifies which characters to use as word boundaries. The following example uses a hyphen as a delimiter:

    >>> s = 'spam-spam-spam'
    >>> delimiter = '-'
    >>> s.split(delimiter)
    ['spam', 'spam', 'spam']

    join is the inverse of split. It takes a list of strings and concatenates the elements. join is a string method, so you have to invoke it on the delimiter and pass the list as a parameter:

    >>> t = ['pining', 'for', 'the', 'fjords']
    >>> delimiter = ' '
    >>> delimiter.join(t)
    'pining for the fjords'

    In this case the delimiter is a space character, so join puts a space between words. To concatenate strings without spaces, you can use the empty string, "", as a delimiter.

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