On 15/11/2007, Timothy Hochberg <[EMAIL PROTECTED]> wrote: > > > On Nov 15, 2007 9:11 AM, Hans Meine <[EMAIL PROTECTED]> wrote: > > Am Donnerstag, 15. November 2007 16:29:12 schrieb Warren Focke: > > > > > On Thu, 15 Nov 2007, George Nurser wrote: > > > > It looks to me like > > > > a,b = (zeros((2,)),)*2 > > > > is equivalent to > > > > x= zeros((2,)) > > > > a,b=(x,)*2 > > > > > > Correct. > > > > > > > If this is indeed a feature rather than a bug, is there an alternative > > > > compact way to allocate many arrays? > > > > > > a, b = [zeros((2,)) for x in range(2)] > > > > Let me add that this is a standard Python caveat, which also happens with > > lists -- many of us have once tried to initialize an array of empty lists > > with ([], ) * N, which results in N references to the same empty list. > > Warren pointed out the standard solution above. > > And I'll just add that another option in this case is to avoid tuples and > lists altogether and just unpack a larger array: > > a, b = zeros([2,2])
Pithy indeed. I didn't realize that one could unpack numpy arrays. > <OFF TOPIC EDITORIAL> > > Using lists for shapes is clearer both typographically: compare zeros((2,)) > and zeros([2]), and conceptually: shapes are closer to lists (variable > length, homogeneous) than tuples (fixed length, inhomogeneous). Tuples are > used for the shape attribute since they need to be immutable, but there's no > reason to type them that way; it just makes things hard to read. > > <OFF TOPIC EDITORIAL> Makes sense. Thanks to everybody for their help. George. _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
