On Mon, 16 Nov 2015 11:27 am, fl wrote: > hi, > > When I learn slice, I have a new question on the help file. If I set: > > pp=a[0:10:2] > > pp is array([1, 3])
Really? How do you get that answer? What is `a`? > I don't know how a[0:10:2] gives array([1, 3]). Neither do I, because you have not told us what `a` is. But I know what `a[0:10:2]` *should* be: it takes a copy of elements from a, starting at position 0, ending just before position 10, and taking every second one. py> a = list(range(100, 121)) py> print(a) [100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120] py> print(a[0:10]) [100, 101, 102, 103, 104, 105, 106, 107, 108, 109] py> print(a[0:10:2]) [100, 102, 104, 106, 108] py> print(a[0:10:3]) [100, 103, 106, 109] By default, the first item is automatically 0, so these two slices are the same: a[0:10:2] a[:10:2] If the start or end position are out of range, the slice will only include positions that actually exist: py> a[:10000:5] [100, 105, 110, 115, 120] -- Steven -- https://mail.python.org/mailman/listinfo/python-list
