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        <div class="PlainText">Hi All,<br>
          <br>
          I just got the problem when I am trying to calculate the flux
          crossing an isocontour flux.<br>
          <br>
          The minimized example looks like this (data dumps are
          generated by Enzo):<br>
          <br>
          >>> ds = load( ‘DD0501/data0501’ )<br>
          >>> dd = ds.all_data()<br>
          >>> flux = dd.calculate_isocontour_flux( 'density',
          1e-, ‘x-velocity’, ‘y-velocity’, ‘z-velocity’, ‘density’ )<br>
          <br>
          Then I got the exception:<br>
          <br>
          ---------------------------------------------------------------------------                                                                                                                       

          [8/936]<br>
          AttributeError                            Traceback (most
          recent call last)<br>
          /u/lilew/Apps/yt-x86_64/src/yt-hg/scripts/iyt in
          <module>()<br>
          ----> 1 flux = sp.calculate_isocontour_flux( 'density',
          rho, 'velocity_x', 'velocity_y', 'velocity_z', 'density' )<br>
          <br>
          /u/lilew/Apps/yt-x86_64/src/yt-hg/yt/data_objects/data_containers.pyc
          in calculate_isocontour_flux(self, field, value, field_x,
          field_y, field_z, fluxing_field)<br>
             1077         """<br>
             1078         flux = 0.0<br>
          -> 1079         for g in self._get_grid_objs():<br>
             1080             flux += self._calculate_flux_in_grid(g,
          field, value,<br>
             1081                     field_x, field_y, field_z,
          fluxing_field)<br>
          <br>
          /u/lilew/Apps/yt-x86_64/src/yt-hg/yt/utilities/parallel_tools/parallel_analysis_interface.pyc
          in _get_grid_objs(self)<br>
             1042         if self._distributed:<br>
             1043             return ParallelObjectIterator(self, True,
          attr='_grids')<br>
          -> 1044         return ObjectIterator(self, True,
          attr='_grids')<br>
             1045<br>
             1046     def get_dependencies(self, fields):<br>
          <br>
          /u/lilew/Apps/yt-x86_64/src/yt-hg/yt/utilities/parallel_tools/parallel_analysis_interface.pyc

          in __init__(self, pobj, just_list, attr)<br>
              123             gs = getattr(pobj, attr)<br>
              124         else:<br>
          --> 125             gs = getattr(pobj._data_source, attr)<br>
              126         if len(gs) == 0:<br>
              127             raise YTNoDataInObjectError(pobj)<br>
          <br>
          AttributeError: 'YTSphere' object has no attribute
          '_data_source'<br>
          <br>
          —————————————————————————————————————    <br>
          <br>
          Could you please help me find out what is wrong? <br>
          <br>
          Any ideas are appreciated. Thanks!<br>
          <br>
          Cheers,<br>
          Lile Wang<br>
          <br>
          <br>
        </div>
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