On Tue, Apr 12, 2011 at 10:27 AM, James Mills
<prolo...@shortcircuit.net.au> wrote:
> This could be simplified to just:
>
> return expr or None
>
> And more to the point... If your calee is relying
> on the result of this function, just returning the
> evaluation of "expr" is enough.
I'm thinking here that that's not a solution; he'll have more code to
follow. An example of what I think he's trying to do:
def fac(n):
# attempt to get from a cache
return? cache[n]
# not in cache, calculate the value
ret=1 if n<=1 else fac(n-1)*n
# and cache and return it
cache[n]=ret; return ret
If the rest of the function can be implemented as an expression, it
might be possible to use:
return expr or other_expr
But in the example of a lookup cache, that wouldn't work so easily -
assignment isn't an expression. If 'x=y' had a value as it does in C,
the above function could become:
def fac(n):
return cache[n] or (cache[n]=1 if n<=1 else fac(n-1)*n)
which is a reasonable one-liner, albeit not the most efficient
factorial implementation. Is there a simple and Pythonic way to do
this?
BTW, assume for the purposes of discussion that the return? expr is a
complex one, such that it's well worth evaluating only once (maybe
even has side effects).
Chris Angelico
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