语法列表加入Python

Question

加入列表的最pythonic方式是什么,以便每个项目之间都有逗号,除了使用"和"的最后一个？

["foo"] --> "foo"
["foo","bar"] --> "foo and bar"
["foo","bar","baz"] --> "foo, bar and baz"
["foo","bar","baz","bah"] --> "foo, bar, baz and bah"

Answer 1

这个表达式做到了:

print ", ".join(data[:-2] + [" and ".join(data[-2:])])

如下所示:

>>> data
    ['foo', 'bar', 'baaz', 'bah']
>>> while data:
...     print ", ".join(data[:-2] + [" and ".join(data[-2:])])
...     data.pop()
...
foo, bar, baaz and bah
foo, bar and baaz
foo and bar
foo

Answer 2

试试这个,它考虑了边缘情况和用途format(),以显示另一种可能的解决方案:

def my_join(lst):
    if not lst:
        return ""
    elif len(lst) == 1:
        return str(lst[0])
    return "{} and {}".format(", ".join(lst[:-1]), lst[-1])

按预期工作:

 my_join([])
=> ""
 my_join(["x"])
=> "x"
 my_join(["x", "y"])
=> "x and y"
 my_join(["x", "y", "z"])
=> "x, y and z"

Answer 3

基于评论的修复导致了这种有趣的方式.它假定要加入的列表的字符串条目中不会出现逗号(无论如何都会出现问题,因此这是一个合理的假设.)

def special_join(my_list):
    return ", ".join(my_list)[::-1].replace(",", "dna ", 1)[::-1]


In [50]: def special_join(my_list):
        return ", ".join(my_list)[::-1].replace(",", "dna ", 1)[::-1]
   ....:

In [51]: special_join(["foo", "bar", "baz", "bah"])
Out[51]: 'foo, bar, baz and bah'

In [52]: special_join(["foo"])
Out[52]: 'foo'

In [53]: special_join(["foo", "bar"])
Out[53]: 'foo and bar'