I was thinking about this in the context of Giudo's comments at scipy 2006 that much of the language is moving away from lists toward iterators. He gave the keys of a dict as an example.
Numpy treats iterators, generators, etc as 0x0 PyObjects rather than lazy generators of n dimensional data. I guess my question for Travis (any others much more expert than I in numpy) is is this intentional or is it something that was never implemented because of the obvious subtlties of defiing the correct semantics to make this work. Personally i find it no big deal to use array(list(iter)) in the 1d case and the list function combined with a list comprehension for the 2d case. I usually know how many dimensions i expect so i find this easy and i know about this peculiar behavior. I find, however, that this behavior is very suprising and confusing to the new user and i don't usually have a good justification for it to answer them. The ideal semantics, in my mind, would be if an iterator of iterators of iterators, etc was no different in numpy than a list of lists of lists, etc. But I have no doubt that there are subtleties i am not considering. Has anyone more familiar than I with the bowels of numpy thought about this problem and see reasons why this is a bad idea or just prohibitively difficult to implement? On 8/27/06, Charles R Harris <[EMAIL PROTECTED]> wrote: > Hi, > > The problem seems to arise in the array constructor, which treats the > generator as a python object and creates an array containing that object. > So, do we want the possibility of an array of generators or should we > interpret it as a sort of list? I vote for that latter. > > Chuck > > > On 8/27/06, Charles R Harris <[EMAIL PROTECTED]> wrote: > > > > Hi Christopher, > > > > > > > > On 8/27/06, Charles R Harris < [EMAIL PROTECTED]> wrote: > > > > > > Hi, > > > > > > > > > > > > On 8/27/06, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > > > -----BEGIN PGP SIGNED MESSAGE----- > > > > Hash: SHA1 > > > > > > > > It seems like numpy.sum breaks generator expressions: > > > > > > > > In [1]: sum(i*i for i in range(10)) > > > > Out[1]: 285 > > > > > > > > In [2]: from numpy import sum > > > > > > > > In [3]: sum(i*i for i in range(10)) > > > > Out[3]: <generator object at 0x10eca58> > > > > > > > > Is this intentional? If so, how do I get the behaviour that I am > after? > > > > > > > > > > > > > > > > > > > > > > In [3]: sum([i*i for i in range(10)]) > > > > > > Out[3]: 285 > > > > > > Chuck > > > > > > > > The numarray.sum also fails to accept a generator as an argument. Because > python does and the imported sum overwrites it, we should probably check the > argument type and make it do the right thing. > > > > Chuck > > > > > > > > > ------------------------------------------------------------------------- > Using Tomcat but need to do more? Need to support web services, security? > Get stuff done quickly with pre-integrated technology to make your job > easier > Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 > > _______________________________________________ > Numpy-discussion mailing list > Numpy-discussion@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/numpy-discussion > > > ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Numpy-discussion mailing list Numpy-discussion@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/numpy-discussion
