Merge pull request #4884 from matthewturk/tipsy_aux_fh

BUG: Fix tipsy file handler opening

yt/frontends/tipsy/io.py

@@ -157,9 +157,12 @@ def _read_particle_data_file(self, data_file, ptf, selector=None):
         f = open(data_file.filename, "rb")
 
         # we need to open all aux files for chunking to work
-        aux_fh = {}
-        for afield in self._aux_fields:
-            aux_fh[afield] = open(data_file.filename + "." + afield, "rb")
+        _aux_fh = {}
+
+        def aux_fh(afield):
+            if afield not in _aux_fh:
+                _aux_fh[afield] = open(data_file.filename + "." + afield, "rb")
+            return _aux_fh[afield]
 
         for ptype, field_list in sorted(ptf.items(), key=lambda a: poff.get(a[0], -1)):
             if data_file.total_particles[ptype] == 0:
@@ -170,19 +173,19 @@ def _read_particle_data_file(self, data_file, ptf, selector=None):
             p = np.fromfile(f, self._pdtypes[ptype], count=count)
             auxdata = []
             for afield in afields:
-                aux_fh[afield].seek(aux_fields_offsets[afield][ptype])
+                aux_fh(afield).seek(aux_fields_offsets[afield][ptype])
                 if isinstance(self._aux_pdtypes[afield], np.dtype):
                     auxdata.append(
                         np.fromfile(
-                            aux_fh[afield], self._aux_pdtypes[afield], count=count
+                            aux_fh(afield), self._aux_pdtypes[afield], count=count
                         )
                     )
                 else:
-                    aux_fh[afield].seek(0)
+                    aux_fh(afield).seek(0)
                     sh = aux_fields_offsets[afield][ptype]
                     if tp[ptype] > 0:
                         aux = np.genfromtxt(
-                            aux_fh[afield], skip_header=sh, max_rows=count
+                            aux_fh(afield), skip_header=sh, max_rows=count
                         )
                         if aux.ndim < 1:
                             aux = np.array([aux])
@@ -209,7 +212,7 @@ def _read_particle_data_file(self, data_file, ptf, selector=None):
 
         # close all file handles
         f.close()
-        for fh in list(aux_fh.values()):
+        for fh in _aux_fh.values():
             fh.close()
 
         return return_data