创建列表叙述字符串的优雅方式

Question

How would you elegantly convert a list with a unknown number of elements into a narrative text representation for user interfaces?

For example:

>>> elements = ['fire', 'water', 'wind', 'earth']

>>> narrative_list(elements)
'fire, water, wind and earth'

Answer 1

def narrative_list(elements):
    last_clause = " and ".join(elements[-2:])
    return ", ".join(elements[:-2] + [last_clause])

which then runs like

>>> narrative_list([])
''
>>> narrative_list(["a"])
'a'
>>> narrative_list(["a", "b"])
'a and b'
>>> narrative_list(["a", "b", "c"])
'a, b and c'

Answer 2

def narrative_list(elements):
    """
    Takes a list of words like: ['fire', 'water', 'wind', 'earth']
    and returns in the form: 'fire, water, wind and earth'
    """
    narrative = map(str, elements)

    if len(narrative) in [0, 1]:
        return ''.join(narrative)

    narrative.append('%s and %s' % (narrative.pop(), narrative.pop()))    
    return ', '.join(narrative)

Answer 3

In python there's very (very) often existing libs to do what you want. Check out humanfriendly https://pypi.python.org/pypi/humanfriendly/1.7.1

>>> import humanfriendly
>>> elements = ['fire', 'water', 'wind', 'earth']
>>> humanfriendly.concatenate(elements)
'fire, water, wind and earth'

I'd only bother with this if you were doing a lot of humanization. Otherwise I like Hugh Bothwell's answer (as it eliminates the third-party dependency from your code).

Answer 4

>>> ', '.join(elements[:-1])+' and '+elements[-1]
'fire, water, wind and earth'

Edit: This would work for a two-elements list, but you might want a special case for one-element lists (or empty lists)

Answer 5

>>> elements = ['fire', 'water', 'wind', 'earth']
>>> ", ".join(elements)[::-1].replace(' ,', ' dna ',1)[::-1]
'fire, water, wind and earth'
>>> elements = ['fire']
>>> ", ".join(elements)[::-1].replace(' ,', ' dna ',1)[::-1]
'fire'
>>> elements = ['fire', 'water']
>>> ", ".join(elements)[::-1].replace(' ,', ' dna ',1)[::-1]
'fire and water'