On 25/08/2010 20:46, Jed wrote:
Hi, I'm seeking help with a fairly simple string processing task.
I've simplified what I'm actually doing into a hypothetical
equivalent.
Suppose I want to take a word in Spanish, and divide it into
individual letters. The problem is that there are a few 2-character
combinations that are considered single letters in Spanish - for
example 'ch', 'll', 'rr'.
Suppose I have:
alphabet = ['a','b','c','ch','d','u','r','rr','o'] #this would include
the whole alphabet but I shortened it here
theword = 'churro'
I would like to split the string 'churro' into a list containing:
'ch','u','rr','o'
So at each letter I want to look ahead and see if it can be combined
with the next letter to make a single 'letter' of the Spanish
alphabet. I think this could be done with a regular expression
passing the list called "alphabet" to re.match() for example, but I'm
not sure how to use the contents of a whole list as a search string in
a regular expression, or if it's even possible. My real application
is a bit more complex than the Spanish alphabet so I'm looking for a
fairly general solution.
You can build a regex with:
>>> '|'.join(alphabet)
'a|b|c|ch|d|u|r|rr|o'
You want to try to match, say, 'ch' before 'c', so you want the longest
first:
>>> '|'.join(sorted(alphabet, key=len, reverse=True))
'ch|rr|a|b|c|d|u|r|o'
If you were going to match the Spanish alphabet then I would recommend
that you do it in Unicode. Well, any text that's not pure ASCII should
be done in Unicode!
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