In article <eae87c72-f62d-4815-bb69-ca862ff78...@googlegroups.com>, Arturo B <a7xrturo...@gmail.com> wrote:
> Hello, I'm making Python mini-projects and now I'm making a Latin Square > > (Latin Square: http://en.wikipedia.org/wiki/Latin_square) > > So, I started watching example code and I found this question on > Stackoverflow: > > http://stackoverflow.com/questions/5313900/generating-cyclic-permutations-redu > ced-latin-squares-in-python > > It uses a list comprenhension to generate the Latin Square, I'm am a newbie > to Python, and I've tried to figure out how this is evaluated: > > a = [1, 2, 3, 4] > n = len(a) > [[a[i - j] for i in range(n)] for j in range(n)] You can re-write any list comprehension as a for loop. In this case you have to un-wrap this one layer at a time. First step: a = [1, 2, 3, 4] n = len(a) temp1 = [] for j in range(n): temp2 = [a[i - j] for i in range(n)] temp1.append(item) then, unwrap the next layer: a = [1, 2, 3, 4] n = len(a) temp1 = [] for j in range(n): temp2 = [] for i in range(n): temp3 = a[i - j] temp2.append(temp3) temp1.append(item) Does that make it any easier to understand? -- https://mail.python.org/mailman/listinfo/python-list
