On 9/12/19 12:27, Musbur wrote:
> Hello,
>
> I have a function with a long if/elif chain that sets a couple of
> variables according to a bunch of test expressions, similar to
> function branch1() below. I never liked that approach much because it
> is clumsy and repetetive, and pylint thinks so as well. I've come up
> with two alternatives which I believe are less efficient due to the
> reasons given in the respective docstrings. Does anybody have a better
> idea?
>
> def branch1(a, b, z):
> """Inelegant, unwieldy, and pylint complains
> about too many branches"""
> if a > 4 and b == 0:
> result = "first"
> elif len(z) < 2:
> result = "second"
> elif b + a == 10:
> result = "third"
> return result
>
> def branch2(a, b, z):
> """Elegant but inefficient because all expressions
> are pre-computed althogh the first one is most likely
> to hit"""
> decision = [
> (a > 4 and b == 0, "first"),
> (len(z) < 2, "second"),
> (b + a == 10, "third")]
> for (test, result) in decision:
> if test: return result
>
> def branch3(a, b, z):
> """Elegant but inefficient because expressions
> need to be parsed each time"""
> decision = [
> ("a > 4 and b == 0", "first"),
> ("len(z) < 2", "second"),
> ("b + a == 10", "third")]
> for (test, result) in decision:
> if eval(test): return result
> (env) [dh@deham01in015:~/python/rscl_fdc/devel]$
>
Well if you really want to go this route, you may consider the following:
def branch4(a, b, z):
decision = [
((lambda: a > 4 and b == 0), "first"),
((lambda: len(z) < 2), "second"),
((lambda: b + a == 10), "third")]
for test, result in decision:
if test(): return result
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