Hello All,
It seems that flex arrays do not support slice assignment:
py> from scitbx.array_family import flex
py> ary = flex.float(range(5))
py> list(ary)
[0.0, 1.0, 2.0, 3.0, 4.0]
py> ary[:3] = flex.float([41, 42, 43])
---------------------------------------------------------------------------
ArgumentError Traceback (most recent call last)
/usr/local/cctbx/cctbx_sources/mmtbx/dynamics/<ipython-input-13-5ce3d648bc6f> in <module>()
----> 1 ary[:3] = flex.float([41, 42, 43])
ArgumentError: Python argument types in
float.__setitem__(float, slice, float)
did not match C++ signature:
__setitem__(scitbx::af::versa > > {lvalue}, scitbx::af::small, float)
__setitem__(scitbx::af::versa > > {lvalue}, long, float)
Slice assignment is common in python:
py> alist = range(5)
py> alist[:3] = [41, 42, 43]
py> alist
[41, 42, 43, 3, 4]
Is there a flex array work-alike for this operation?
I've found set_selected():
py> sel_ary = flex.bool([True, True, True, False, False])
py> ary.set_selected(sel_ary, flex.float([41, 42, 43]))
py> list(ary)
[41.0, 42.0, 43.0, 3.0, 4.0]
But set_selected() is cumbersome for slice assignment because (1) you have to build a flex selection array somehow and (2) you have to put the new values into a flex array of the appropriate type. Is set_selected() the best way? If so, is there something in the cctbx libraries that makes building "slicing" selection arrays more efficient than say a list comprehension?
sel_ary = flex.bool([True if i < 3 else False for i in xrange(5)])
James
