I have the following code, I was wondering if I can convert it to single line for loop?
for a,b in myList :
sth = calcSth(a, b)
if sth > 60 :
return True
return False
another question is: is there any difference in the performance of single line for loop and block-code for loop?
you can replace your whole loop by this oneliner (is this really a oneliner when using if on a single line?):
if any(calcSth(a,b)>60 for a,b in myList): return True
any will stop testing as soon as a a,b matches the condition.
Also, according to your last edit, if you're planning to return False right after your loop if nothing matches, you can replace the whole routine by:
return any(calcSth(a,b)>60 for a,b in myList)
EDIT: about the performance, I made a quick test, and as predicted, the any construct is roughly 20% faster with the input data I provided (35 items and matching condition in the end, kind of "worst case"). If the matching condition is at the beginning of the list, the difference is very small between both constructions.
any(calcSth(a, b) ...in myList) is fine syntax. Parenthesis are needed only if the generator is not the only argument to a function call.
return any(x(a,b)>60 for a,b in myList) if he wants to return False if it fails, OP isn't clearMaybe something like this (modified):
from itertools import starmap
list(filter(lambda x: x > 60, starmap(calcSth, myList))) != []
or, if you don't like to evaluate the full list
from itertools import starmap, islice
list(islice(filter(lambda x: x > 60, starmap(calcSth, myList)), 1)) != []
The last one will stop after the first value that is larger than 60.
False because a filter object is different from all lists. Only in python2 this can work, but the question is not tagged python2...return statement and drop the test against empty list. If not empty, just testing the list will yield True. +1 for the starmap stuff. But I'm not sure that creating a list just to consume the filter is very good for performance.
Strictly speaking, I don't believe there is a single-line equivalent to your posted code. As Jean-Francois answered, you can replace the loop block with a single line, but not the return.
return Falseat the end:return any(calcSth(a,b)>60 for a,b in myList)