On 12/15/11 10:48, Roy Smith wrote:
I've got a list, ['a', 'b', 'c', 'd']. I want to generate the string, "a, b, c, and
d" (I'll settle for no comma after 'c'). Is there some standard way to do this,
handling all the special cases?
[] ==> ''
['a'] ==> 'a'
['a', 'b'] ==> 'a and b'
['a', 'b', 'c', 'd'] ==> 'a, b, and c'
It seems like the kind of thing django.contrib.humanize would handle, but alas,
it doesn't.
If you have a list, it's pretty easy as MRAB suggests. For
arbitrary iterators, it's a bit more complex. Especially with
the odd edge-case of 2 items where there's no comma before the
conjunction (where >2 has the comma before the conjunction). If
you were willing to forgo the Oxford comma, it would tidy up the
code a bit. Sample code below
-tkc
def gen_list(i, conjunction="and"):
i = iter(i)
first = i.next()
try:
prev = i.next()
except StopIteration:
yield first
else:
more_than_two = False
for item in i:
if not more_than_two: yield first
yield prev
prev = item
more_than_two = True
if more_than_two:
yield "%s %s" % (conjunction, prev)
else:
yield "%s %s %s" % (first, conjunction, prev)
def listify(lst, conjunction="and"):
return ', '.join(gen_list(lst, conjunction))
for test, expected in (
([], ''),
(['a'], 'a'),
(['a', 'b'], 'a and b'),
(['a', 'b', 'c'], 'a, b, and c'),
(['a', 'b', 'c', 'd'], 'a, b, c, and d'),
):
result = listify(test)
print "%r -> %r (got %r) %s" % (
test, expected, result,
result == expected and "PASSED" or "FAILED"
)
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