On Wed, Mar 9, 2016 at 7:06 AM, Pavol Lisy pavol.lisy@gmail.com wrote:
2016-03-08 15:17 GMT+01:00, Allan Clark allan.clark@gmail.com: [...]
[y for x in numbers if abs(x) as y > 5][...]
* It would need to be decided whether you allowed multiple 'as'expression in the condition, particularly using 'and' or 'or' as in 'if f(a) as x > 5 and f(b) as y > 5'
Just small idea not to forget here:
[y+z for x in numbers if abs(x) as y > 5 or x**2 as z>100]
"or" is short-circuit operator so z could be not (well) defined.
Enforcing that the order of operations is as you're implying:
[y+z for x in numbers if (abs(x) as y) > 5 or (x**2 as z) > 100]
If the first condition is true, the second will not be evaluated. It'll be equivalent to:
def <listcomp>(): result = [] for x in numbers: y = abs(x) if y > 5: result.append(y+z) else: z = x**2 if z > 100: result.append(y+z) return result
So, yeah, that could surprise a *lot* of people. Either an UnboundLocalError, or retaining the value from the previous iteration.
Recommendation: If you use name bindings in the second half, use bitwise operators instead:
[y+z for x in numbers if (abs(x) as y) > 5 | (x**2 as z) > 100]
That'll force both sides to be evaluated. (Downside: It's reliable only if you actually have True and False.)
ChrisA