Comments on: An Academic Inconvenience of Python

By: Caching Dictionaries in Python vs. Ruby - Push cx

Caching Dictionaries in Python vs. Ruby - Push cx — Sat, 02 Feb 2008 18:02:05 +0000

[...] A while ago I made a slightly-underinformed post (see the corrections in the comments) trying to draw a difference between Python and Ruby. I’ve finally got a decent example and can explain what I’m getting at. [...]

By: Jim Storch

Jim Storch — Fri, 09 Nov 2007 19:42:16 +0000

Oops, one too many characters. Make that:

^(.{,254}[.!?])

By: Jim Storch

Jim Storch — Fri, 09 Nov 2007 14:33:03 +0000

If you want to use regular expressions, this should do the trick:

^(.{,255}[.!?])

I’m not the fan of clever one-liners that I used to be. They seem out of place in Python.

Cheers.

By: Phil Hassey

Phil Hassey — Thu, 08 Nov 2007 17:51:25 +0000

A shorter way (that works):

s[:max([s.rfind(c,0,255) for c in ".!?"])+1]

By: Kevin

Kevin — Thu, 08 Nov 2007 17:19:45 +0000

Academic roots of Python the problem. Nah. First of all your example is missing a right paren to close the max function. Next, I just don’t see how your logic is going to work, maybe I’m missing something, but it looks to me that the value of s in the right index is going refer to the original longer string. rfind seems to be a better choice. This or a variant seems to be closer to to what your looking for:
s[:max(s[:255].rfind(‘.’), s[:255].rfind(‘!’), s[:255].find(‘?’))+1]
A little clunkier, but it seems to work.

By: Peter Harkins

Peter Harkins — Thu, 08 Nov 2007 17:17:05 +0000

John: Yeah, you’re right. I just tested and found I had to write:

 
s[:max(s[:255].rfind("."), s[:255].rfind("!"), s[:255].rfind("?")) + 1]

The code was slightly different in the script I wrote (two lines, had a temp var) for unrelated actions and I ran it together for the post.

By: Daivd

Daivd — Thu, 08 Nov 2007 17:04:13 +0000

This is why the regexp module (re) exists (and rfind as others have pointed out). If you had to use rindex, you could do the hack approach and prepend the string with ‘!?.’ :)

By: John Carr

John Carr — Thu, 08 Nov 2007 16:58:37 +0000

Can you really use s like that? Consider which of these 2 variants – which would python execute internally?

a = s[:255]
s = [:max(a.rfind(’.'), a.rfind(’!'), a.rfind(’x') + 1)]

a = s[:255]
s = [:max(s.rfind(’.'), s.rfind(’!'), s.rfind(’x') + 1)]

If ‘s’ somehow mutates halfway through the statement i’d consider it somewhat broken, but in order for your one-liner to work.. it would have to ?!?

By: Doug Winter

Doug Winter — Thu, 08 Nov 2007 16:40:36 +0000

re.sub(‘[^\.\!\?]+$’, ”, s[:255])

By: James B.

James B. — Thu, 08 Nov 2007 16:40:27 +0000

Wouldn’t using rfind instead of rindex work? It returns -1 when not found rather than raising an exception, and it is even one character less to type!

By: Peter Harkins

Peter Harkins — Thu, 08 Nov 2007 16:38:13 +0000

Phil: Wow, I completely missed rfind. That does indeed work exactly the way I wanted.

Tiberiu: Yeah, I go back and forth over how paranoid I want the language to be about these things by default. I also learned Python after PHP and I saw a lot of PHP bugs come from it being especially “helpful” by coercing types and not complaining about discrepancies.

By: Tiberiu Ichim

Tiberiu Ichim — Thu, 08 Nov 2007 16:32:13 +0000

Long, long time ago, when I was came to Python from the PHP world I’ve appreciated Python for exactly this type of behaviour: don’t return stupid “default” values, and instead raise errors when something is not according to the programmer’s wishes.

I, myself, prefer a somewhat longer code, but one that is more easily understood at first glance.

By: phil hassey

phil hassey — Thu, 08 Nov 2007 16:19:25 +0000

you might try: s = s[:255][:max(s.rfind("."), s.rfind("!"), s.rfind("?")) + 1]