Re: [Python-ideas] FInd first tuple argument for str.find and str.index
Guido> On 9/4/07, Ron Adam <rrr@ronadam.com> wrote:
Could we add the ability of str.index and str.find to accept a tuple as the first argument and return the index of the first item found in it.
Hi If someone is going to head down this path, it might be better to implement a more general algorithm and provide the above as a special case via an argument. There's a fast and beautiful algorithm due to Aho & Corasick (CACM, 1975) that finds _all_ matches of a set of patterns. It runs in time that's linear in max(sum of the lengths of the patterns to be matched, length of to-be-matched text). The algorithm was the basis of fgrep. To provide the above, a special case could have it return as soon as it found a first match (i.e., of any pattern). One general way to write it would be to have it return a dict of patterns and result indices in the case that the pattern argument is a tuple. So "Hey, look, look, look at these patterns".find(('look', 'for', 'these', 'patterns')) might return { 'look' : [ 5, 11, 17 ], 'for' : [ ], # or arguably [ -1 ], 'these' : [ 25 ], 'patterns' : [ 31 ], } OK, that's a bit of a departure from the normal behavior of find, but so is passing a tuple of patterns. Alternately, you could also get back a tuple of (tuples of) matching indices. The ideal calling interface and result depends on what you need to do - check if a specific string matched? Just know the first match offset, etc. I don't know the best solution, but the algorithm rocks. Raymond - you'll love it :-) Terry
participants (2)
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Mathias Panzenböck -
Terry Jones