numpy.fromiter: matrix from fixed-length arrays

gistfile1.py

# Even more fun
def array_gen(some_strings):
    for s in some_strings:
        yield numpy.fromstring(s, dtype=numpy.int)

# Let's say I know the length of all the arrays coming out of my generator
# and I want to build a matrix

K = 10
M = 5

stringified = numpy.arange(K).tostring()
str_gen = (stringified for i in xrange(M))    # This is just a generator object, hasn't done anything yet
m = numpy.fromiter(array_gen(str_gen), dtype=[('cool', numpy.int, K)])

"""
The array would look like this:
>>> m

array([([0, 1, 2, 3, 4, 5, 6, 7, 8, 9],),
       ([0, 1, 2, 3, 4, 5, 6, 7, 8, 9],),
       ([0, 1, 2, 3, 4, 5, 6, 7, 8, 9],),
       ([0, 1, 2, 3, 4, 5, 6, 7, 8, 9],),
       ([0, 1, 2, 3, 4, 5, 6, 7, 8, 9],)], 
      dtype=[('cool', ''<i8', 10)])

>>> m.flags.owndata
True

....But you can also access the single matrix through the 'cool' index without making copies (uses views)

>>> m['cool']

array([[0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
       [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
       [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
       [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
       [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]])

>>> m.flags.owndata
False


"""