numpy/numpy — pull request #4567 by juliantaylor (2014-03-28 20:14:14+00:00)
Title: ENH: optimize array creation from homogenous python sequences

Instead calling PyArray_DTypeFromObjectHelper for each item in a
sequence, check if all items in the sequence are of the same scalar
type, if this is the case we only need to recurse on one item.
Also use the PySequence_Fast API to avoid expensive function calls for
the common case of lists or tuples.

np.array(range(10)) improves about 25%
np.array(range(100)) improves about 40%