>Is this what you want? > >>>> [[j for j in range(i*2, 50, i)] for i in range(2,8)] >[[4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48], [6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, 48], [8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48], [10, >15, 20, 25, 30, 35, 40, 45], [12, 18, 24, 30, 36, 42, 48], [14, 21, 28, 35, 42, 49]]
>[I am not sure what you are trying -- just making local changes to the ZF to make it work] >https://mail.python.org/mailman/listinfo/python-list Yes, awesome. Thanks. But it breaks all the picture that I've built in my head about comps till now... As I know from books and googling, the comps main idea looks approximately like this: [target <--main loop<--nested loop/s (and maybe some conditions)] Am I right? But your code looks somehow inverted to me o_0 Like: [[target with nested loop] <--- main loop with initial values for target] On the other hand, if I'm comparing to my tryouts: noprimes = [[j for i in range(2, 8)] for j in range(i*2, 50, i)] It looks same but the variables are not separated, so it definitely was not defined.... Sincerely, Ivan -----Original Message----- From: Python-list [mailto:python-list-bounces+webmailgroups=gmail....@python.org] On Behalf Of Rustom Mody Sent: Sunday, November 23, 2014 17:09 To: python-list@python.org Subject: Re: Comprehension with two variables - explanation needed On Sunday, November 23, 2014 8:28:16 PM UTC+5:30, Ivan Evstegneev wrote: > Hello guys, > > I would like to ask you for some explanations on comprehensions. > (Don't be scared, it just some particular example ^_^) > > I found this little "find prime number" example over the internet: > > >>> noprimes = [j for i in range(2, 8) for j in range(i*2, 50, i)] > >>> primes = [x for x in range(2, 50) if x not in noprimes] print > >>> primes > [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47] > > > It looked pretty clear to me, till the time I decided to make some > changes to it %))) > > Ok this is the case: > > As you can see the first line's comprehension produces a list, that includes all the multiplications of "i" (that range(2,8) ) in range (i*2, 50, i). > So I get this pattern: noprimes = = [4, 6, 8.....48, 6, 9,12.... ]. > The change that I tried to apply to this comprehension would lead to > the following pattern: noprimes = = [[4, 6,8...48], [6, 9, 12....], > ....,[some numbers]] > > But despite my struggling on it for the whole day, I haven't got to > the desirable result(using comprehensions only) > > Please, don't get me wrong, I'm not a lazy one (just a beginner). > > In my case, I made some googling, and found some patterns for matrices, that look this one(for example): > > Matrix = [[0 for x in range(5)] for x in range(5)] > > But when I tried to use square brackets with my code, it yields an error about definition of "i", for instance: > > File "<pyshell#30>", line 1, in <module> noprimes = [[j for i in > range(2, 8)] for j in range(i*2, 50, i)] > NameError: name 'i' is not defined. Is this what you want? >>> [[j for j in range(i*2, 50, i)] for i in range(2,8)] [[4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48], [6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, 48], [8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48], [10, 15, 20, 25, 30, 35, 40, 45], [12, 18, 24, 30, 36, 42, 48], [14, 21, 28, 35, 42, 49]] [I am not sure what you are trying -- just making local changes to the ZF to make it work] -- https://mail.python.org/mailman/listinfo/python-list -- https://mail.python.org/mailman/listinfo/python-list
