On Wed, 27 Feb 2008 14:41:32 -0600, Tim Chase wrote:
>>> Is there an easy way to make string-formatting smart enough to
>>> gracefully handle iterators/generators? E.g.
>>>
>>> transform = lambda s: s.upper()
>>> pair = ('hello', 'world')
>>> print "%s, %s" % pair # works
>>> print "%s, %s" % map(transform, pair) # fails
>>>
>>> with a """
>>> TypeError: not enough arguments for format string """
[snip]
I think there is a good case for % taking an iterator. Here's an
artificial example:
def spam():
while True: yield "spam"
spam = spam()
"%s eggs tomato and %s" % spam
"%s %s bacon tomato %s and eggs" % spam
"%s %s %s %s %s %s %s %s truffles and %s" % spam
The iterator could be arbitrarily complex, but the important feature is
that the % operator lazily demands values from it, taking only as few as
it needs. If the iterator is exhausted early, it is an error.
[...]
>> So the answer is always use tuple(...) as others pointed.
>
> I'll adjust my thinking on the matter, and mentally deprecate map() as
> well.
map() isn't deprecated, not even for Python 3 where it remains a built-
in. However it will return an iterator instead of a list, making it
(presumably) a more convenient way to spell itertools.imap().
--
Steven
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