Need a specific sort of string modification. Can someone help?
roy at panix.com
Sat Jan 5 16:38:54 CET 2013
In article <mailman.121.1357398573.2939.python-list at python.org>,
Chris Angelico <rosuav at gmail.com> wrote:
> it may or may not run faster than the explicit state machine,
Hmmm, hard to say. Both are O(n), but yours makes several more copies
of the data than mine (the string addition, the replace(), the split(),
the string slicing). We both make copies as we put fragments into a
list, and when we do the join().
On the other hand, yours does all that inside the library, which is
generally faster than random python code.
You got me by a factor of 3 or 4. Not bad. And not terribly
surprising. Once you've got things to the same O() group, pushing as
much data manipulation as you can down into the library is usually a
pretty effective optimization technique.
> but IMHO it's a lot clearer to read a split() than something
> that changes state when a particular character is found.
Maybe. But being familiar with state machines is still a handy skill.
DNA sequence analysis has lots of problems like "find a start codon
which is within about 50 bases of a binding site, and then copy
everything up until you find a stop codon". Things like that often map
well to state machines. Especially if you're trying to do it in
parallel in all three reading frames.
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