whats the best way to join an array into a readable list

Question

I've got an array listing days of the week:

days = ['Monday', 'Tuesday', 'Wednesday']

Whats the easiest / best way to output it in a human readable format:

Monday, Tuesday and Wednesday

The best I have is a rather ugly:

', '.join(days[:-2]+['']) + ' and '.join(days[-2:])

Answer 1

One example, from Supybot

Answer 2

Here is what I would do:

'%s and %s' % (', '.join(days[:-1]), days[-1])

Not sure its pretty, but not sure it has to be either. :)

Answer 3

you really don't need that second join() in your 'best' sample. you can rewrite it this way:

', '.join(days[:-1])+' and '+days[-1]

personally, i always prefer calling the class method, because i find the syntax closer to the intent:

str.join(', ',days[:-1])+' and '+days[-1]

Answer 4

I would make a lambda/function once and then just re-use it.

def days(*d):
    ''.join([i + ((n < len(d) - 2 and ', ') or ' and ') for n, i in enumerate(d)])[:-5] + '.'

print days('Monday', 'Tuesday', 'Wednesday')
>>> Monday, Tuesday and Wednesday.

print days('Monday', 'Tuesday')
>>> Monday and Tuesday.

print days('Monday', 'Tuesday')
>>> Monday.

Works for every combination too :)

Answer 5

Why is everyone trying to force-fit this into a single expression?

def comma_separated(lst):
    """
    >>> comma_separated(['a'])
    'a'
    >>> comma_separated(['a', 'b'])
    'a and b'
    >>> comma_separated(['a', 'b', 'c'])
    'a, b and c'
    """
    if len(lst) == 1:
        return lst[0]
    comma_part = ", ".join(lst[:-1])
    return "%s and %s" % (comma_part, lst[-1])

if __name__ == "__main__":
    import doctest
    doctest.testmod()

And remember, this is specific to English (and aside from "and", probably some other Western languages). Other languages have entirely different rules.