"Andy Dingley" <[EMAIL PROTECTED]> writes:
> I'm trying to write rot13, but to do it in a better and more Pythonic
> style than I'm currrently using. What would you reckon to the
> following pretty ugly thing? How would you improve it? In
> particular, I don't like the way a three-way selection is done by
> nesting two binary selections. Also I dislike stating the same
> algorithm twice, but can't see how to parameterise them neatly.
It looks to me like a good place to use closure and dictionaries.
I would write it this way:
def rot(step):
import string
rot_char = lambda a,c,step=step: chr((((ord(c) - ord(a)) + step) % 26) +
ord(a))
make_dict = lambda a,s: dict([(x, rot_char(a, x)) for x in s])
d = make_dict('a', string.ascii_lowercase)
d.update(make_dict('A', string.ascii_uppercase))
def f(s):
return "".join([d.get(c) or c for c in s])
return f
>>> rot13 = rot(13)
>>> rot13('Sybevk Tenohaqnr, Fcyhaqvt ihe guevtt')
'Florix Grabundae, Splundig vur thrigg'
>>> rot_13 = rot(-13)
>>> rot_13('Florix Grabundae, Splundig vur thrigg')
'Sybevk Tenohaqnr, Fcyhaqvt ihe guevtt'
--
HTH,
Rob
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