Joining elements into a string

[Charles]

So Python let's you say:

Code: Select all

print ", ".join(items)

But I always found that rather strange as I think first about the items. Also it disallows having two separators such as ", " but with "and" for the last separator. So I'm planning:

print items.joined(", ")
print words.joined(", ", " and ")

I think one of the problems in Python is that there is no common base type for "list-like objects" but in .NET and JVM we can put an extension method on IEnumerable/Iterable.

[Csaba]

Hi, good idea, it would be easier to understand and nicer! Regards Csaba

[Charles]

This is now in the standard library as an extension to IEnumerable:

extend System.Collections.IEnumerable

    def join(sep as String) as String
        """
        Join the items in an IEnumerable collection separated by a string.
        """
        test
            assert ['a', 'b'].join('.') == 'a.b'
            assert ['a'].join('.') == 'a'
            assert [1, 2].join(', ') == '1, 2'
            assert [1, 2].join('') == '12'
            assert [].join('.') == ''
        body
            # ...

    def join(sep as String, lastSep as String) as String
        """
        Join the items in an IEnumerable collection with a separator string except for the last
        two items; join them with the lastSep string
        """
        test
            assert ['a', 'b'].join(', ', ' and ') == 'a and b'
            assert ['a', 'b', 'c'].join(', ', ' and ') == 'a, b and c'
            assert ['a', 'b', 'c', 'd'].join(', ', ' and ') == 'a, b, c and d'
            assert [1, 2, 3, 4].join(', ', ' and ') == '1, 2, 3 and 4'
            assert [1].join('.', ':') == '1'
            assert [1, 2].join('', '') == '12'
            assert [].join('.', ':') == ''
        body
            # ...

[jonathandavid]

Very cool, this is much better than Python's approach IMHO.

I think it could be useful as well to have a version that takes the "initial" separator, so we can make:

assert [1, 2, 3, 4].join('{', ':', '}') == '{1:2:3:4}'