Sorry for chiming in so late; I was lurking using google groups and had to subscribe to post - hence this new thread.
I gather that *where* has been discarded as a possible new keywords given its use as a function in numpy ( https://docs.scipy.org/doc/numpy-1.14.0/reference/generated/numpy.where.html) ... Still, I will include it below for completeness (and as I think it reads better than the other choices) Here are two sets of two examples illustrating a situation that I have not seen before, and which read (to me) much better when using a keyword (given or where) than a symbol (:=). Furthermore, the position of the temporary assignment can, in my opinion, be done differently and help in making the code clearer. First example: single temporary assignment, done four different ways. 1) using := real_roots = [ (-b/(2*a) + (D:= sqrt( (b/(2*a))**2 - c/a), -b/(2*a) - D) for a in range(10) for b in range(10) for c in range(10) if D >= 0] 2) using *given* at the very end real_roots = [ (-b/(2*a) + D, -b/(2*a) - D) for a in range(10) for b in range(10) for c in range(10) if D >= 0 given D= sqrt( (b/(2*a))**2 - c/a)] 3) using *given* before the iterations real_roots = [ (-b/(2*a) + D, -b/(2*a) - D) given D= sqrt( (b/(2*a))**2 - c/a) for a in range(10) for b in range(10) for c in range(10) if D >= 0] 4) using *where* before the iterations (which would be my preferred choice if it were available) real_roots = [ (-b/(2*a) + D, -b/(2*a) - D) where D= sqrt( (b/(2*a))**2 - c/a) for a in range(10) for b in range(10) for c in range(10) if D >= 0] Second example: multiple assignments. When we have multiple temporary assignments, the situation can be more complicated. In the following series of examples, I will start in reverse order compared to above. 5) using *where* before the iterations real_roots2 = [ (-b/(2*a) + D, -b/(2*a) - D) where D= sqrt( (b/(2*a))**2 - c/a) where c = c_values/100 for c_values in range(1000) if D >= 0] 6) using *given* before the iterations real_roots2 = [ (-b/(2*a) + D, -b/(2*a) - D) given D= sqrt( (b/(2*a))**2 - c/a) given c = c_values/100 for c_values in range(1000) if D >= 0] 7) using *given* at the very end real_roots2 = [ (-b/(2*a) + D, -b/(2*a) - D) for c_values in range(1000) if D >= 0 given D= sqrt( (b/(2*a))**2 - c/a) given c = c_values/100] 8) Using := real_roots2 = [ ( -b/(2*a) + (D:= sqrt( (b/(2*a))**2 - (c:=c_values/100)/a), -b/(2*a) - D) for c_values in range(1000) if D >= 0] I find this last version extremely difficult to understand compared with the others where a keyword is used. Perhaps it is because I do not fully understand how := should be used... Finally ... if "where" cannot be used, given the very special status of such temporary assignments, could "where_" (with a trailing underscore) be considered? I would argue that any word followed by an underscore would be more readable than a compound symbol such as ":=". André
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