How do I find the longest string in Python?

Question

Something like max(len(s1), len(s2)) will only return the maximum length. But if I actually want to find out which string is longer, and perhaps save it to another string, how is that done? max(s1,s2) seems to return the string with the larger value, but not necessarily the longest.

Note: this has to be done without lists or arrays.

Claudiu · Accepted Answer · 2012-09-21 21:47:16Z

39

max takes a key function which causes max to take the max key(val) for each val, yet still return the val, to wit:

>>> max("foobar", "angstalot")
'foobar'
>>> max("foobar", "angstalot", key=len)
'angstalot'

answered Sep 21, 2012 at 21:47

Claudiu

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1 Comment

Rajesh Mappu Over a year ago

>>> max("foobar", "foobak", key=len) >>> 'foobar' max might not be best solution here?

Joe · Accepted Answer · 2012-09-21 21:47:29Z

1

def longest(a, b):
   if len(a) > len(b):
       return a
   return b

answered Sep 21, 2012 at 21:47

Joe

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9 Comments

user395760 Over a year ago

It works, but it's not idiomatic because precisely that functionality, in a more general and useful form, already exists among the builtins.

Joe Over a year ago

Maybe you should edit the question to say "what is the one true way to do this?".

user395760 Over a year ago

It's neither my downvote nor my question. But apart from that, a downvote does not mean "the answer doesn't address the letter of the question" but "the answer is not useful". And it arguably isn't, because it teaches unassuming readers to re-implement basic functionality instead of using the built in functions.

Joe Over a year ago

Fair enough. I agree that using the built-in is more 'pythonic' but disagree that a non-one-liner is not useful where a one-liner is available.

user395760 Over a year ago

It's not about one liners (more often than not that leads to less readable code), but about re-implementing using four lines for something which is can be stated clearer, better and more general in less code.

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martineau · Accepted Answer · 2012-09-23 14:19:30Z

1

Just a simple conditional expression based on the length of each string is all that is needed:

longest = s1 if len(s1) > len(s2) else s2

edited Sep 23, 2012 at 14:19

answered Sep 21, 2012 at 21:58

martineau

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