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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi Folks,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">While we’re on the subject of array slice assignment: it would be really cute if the numpy-style assignment would also work viz:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> image = self._reader.read(index)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> array[k,:,:] = image.as_numpy_array()[y0:y1, x0:x1]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">so we could avoid using numpy arrays in dxtbx ;o)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Any ideas?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Graeme<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> cctbxbb-bounces@phenix-online.org [mailto:cctbxbb-bounces@phenix-online.org]
<b>On Behalf Of </b>James Stroud<br>
<b>Sent:</b> 11 April 2013 08:49<br>
<b>To:</b> cctbx mailing list<br>
<b>Subject:</b> [cctbxbb] Flex array slice assignment work-alike<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:13.5pt">Hello All,</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:13.5pt">It seems that flex arrays do not support slice assignment:</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">py> from scitbx.array_family import flex</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">py> ary = flex.float(range(5))</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">py> list(ary)</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">[0.0, 1.0, 2.0, 3.0, 4.0]</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">py> ary[:3] = flex.float([41, 42, 43])<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">---------------------------------------------------------------------------<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">ArgumentError Traceback (most recent call last)<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">/usr/local/cctbx/cctbx_sources/mmtbx/dynamics/<ipython-input-13-5ce3d648bc6f> in <module>()<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">----> 1 ary[:3] = flex.float([41, 42, 43])<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif""><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">ArgumentError: Python argument types in<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif""> float.__setitem__(float, slice, float)<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">did not match C++ signature:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif""> __setitem__(scitbx::af::versa<float, scitbx::af::flex_grid<scitbx::af::small<long, 10ul> > > {lvalue}, scitbx::af::small<long, 10ul>, float)<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif""> __setitem__(scitbx::af::versa<float, scitbx::af::flex_grid<scitbx::af::small<long, 10ul> > > {lvalue}, long, float)<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span class="apple-style-span"><span style="font-size:18.0pt">Slice assignment is common in python:</span></span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">py> alist = range(5)</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">py> alist[:3] = [41, 42, 43]</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">py> alist</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">[41, 42, 43, 3, 4]</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:13.5pt">Is there a flex array work-alike for this operation?</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:13.5pt">I've found set_selected():</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">py> sel_ary = flex.bool([True, True, True, False, False])</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">py> ary.set_selected(sel_ary, flex.float([41, 42, 43]))</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif""><scitbx_array_family_flex_ext.float at 0x101df1158></span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">py> list(ary)</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">[41.0, 42.0, 43.0, 3.0, 4.0]</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:13.5pt">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?</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Monaco","serif"">sel_ary = flex.bool([True if i < 3 else False for i in xrange(5)])</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:13.5pt">James</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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