numpy not working with itertools.chain objects (Trac #1005) #1603
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trac user rogerbrent wrote on 2009-02-12 Is there a recommended way to use numpy.sum() with a chain iterator that returns numpy arrays? Also, is there a reason why array()/sum() work with normal iterators but not with itertools.chain? |
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@rkern wrote on 2009-02-12 Generally, iterators are not supported as arguments to array(). Use fromiter() instead. There isn't a good way to implement array() to take iterators, too. fromiter() makes some assumptions in order to support this for 1D iterators of scalars, but array() cannot make these assumptions. |
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@rkern wrote on 2009-02-12 You can just use the builtin sum() function. array() does not work with normal iterators, just sequences. xrange(), for example, is a sequence, not an iterator. It has If you want to talk about it more, please ask on the mailing list. Trac tickets aren't good for back-and-forth conversations. |
Original ticket http://projects.scipy.org/numpy/ticket/1005 on 2009-02-11 by trac user rogerbrent, assigned to unknown.
numpy.array(), numpy.sum(), etc. don't seem to work with itertools.chain objects.
e.g.:
from itertools import chain
iter = chain(xrange(5))
array(iter)
returns array(<itertools.chain object at 0x0172C828>, dtype=object).
list(iter) would work as expected, returning [0, 1, 2, 3, 4].
However if I define my own chain() function then array(iter) works fine.
Python v2.5.4 and numpy v1.2.1
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