"Chinook" wrote: > I'm probably just getting languages mixed up, but I thought in my Python > readings over the last couple months that I had noticed an either/or > expression (as opposed to a bitwise or, or truth test). Being a curious > sort, I tried several variations of how a list comprehension *might* be > constructed and got the results expected relative to the operators, but > not the results I was trying to achieve. > > So, is it possible to achieve what the "for loop" (below) does in a > single list comprehension? I don't even see a way to accomplish such in > two list comprehensions with an intermediate result unless an index > pattern was the criterion. > > Just wondering, > Lee C > > PS I'm not suggesting it be added to the language :~) Beyond the new > classes and decorators (simply a convienence), I'm for KISS even to the > extent of the much abused Case statement. > > >>> ta = [5, 15, 12, 10, 9] > >>> for i in range(len(ta)): > ... if ta[i] >= 10: > ... ta[i] -= 10 > ... else: > ... ta[i] += 10 > ... > >>> ta > [15, 5, 2, 0, 19]
The following works, although its readability is debatable, to say the least, let alone performance in the general worst case: >>> ta = [5, 15, 12, 10, 9] >>> ta = [(x+10,x-10)[x>=10] for x in ta] >>> ta > [15, 5, 2, 0, 19] The lack of a ternary if?then:else operator manifests itself in such examples, but alas, there isn't much hope that even python 3K will have one... Would-go-with-ugly-syntax-than-no-syntax-any-day'ly yrs, George -- http://mail.python.org/mailman/listinfo/python-list
