New issue 773: Unitrefactor: cannot process units for magnetic fields https://bitbucket.org/yt_analysis/yt/issue/773/unitrefactor-cannot-process-u... John ZuHone: This script: ``` #!python pf = load("GasSloshing/sloshing_nomag2_hdf5_plt_cnt_0100") v, c = pf.h.find_max("density") sl = pf.h.slice(0, c[0]) print sl["magnetic_field_z"].shape ``` results in this: ``` --------------------------------------------------------------------------- UnitParseError Traceback (most recent call last) <ipython-input-3-9aa7caa31868> in <module>() 5 print sl["z"] 6 print sl["pdx"] ----> 7 print sl["magnetic_field_z"].shape /Users/jzuhone/Source/yt-units-notbroke/yt/data_objects/data_containers.pyc in __getitem__(self, key) 203 return self.field_data[f] 204 else: --> 205 self.get_data(f) 206 # fi.units is the unit expression string. We depend on the registry 207 # hanging off the dataset to define this unit object. /Users/jzuhone/Source/yt-units-notbroke/yt/data_objects/data_containers.pyc in get_data(self, fields) 607 608 fields_to_generate += gen_fluids + gen_particles --> 609 self._generate_fields(fields_to_generate) 610 611 def _generate_fields(self, fields_to_generate): /Users/jzuhone/Source/yt-units-notbroke/yt/data_objects/data_containers.pyc in _generate_fields(self, fields_to_generate) 630 raise RuntimeError 631 self.field_data[field] = fd --> 632 fd.convert_to_units(fi.units) 633 except GenerationInProgress as gip: 634 for f in gip.fields: /Users/jzuhone/Source/yt-units-notbroke/yt/units/yt_array.pyc in convert_to_units(self, units) 330 331 """ --> 332 new_units = self._unit_repr_check_same(units) 333 conversion_factor = self.units.get_conversion_factor(new_units) 334 /Users/jzuhone/Source/yt-units-notbroke/yt/units/yt_array.pyc in _unit_repr_check_same(self, units) 312 # let Unit() handle units arg if it's not already a Unit obj. 313 if not isinstance(units, Unit): --> 314 units = Unit(units, registry = self.units.registry) 315 316 if not self.units.same_dimensions_as(units): /Users/jzuhone/Source/yt-units-notbroke/yt/units/unit_object.pyc in __new__(cls, unit_expr, cgs_value, dimensions, registry, **assumptions) 133 else: 134 # lookup the unit symbols --> 135 cgs_value, dimensions = _get_unit_data_from_expr(unit_expr, registry.lut) 136 137 # Sympy trick to get dimensions powers as Rationals /Users/jzuhone/Source/yt-units-notbroke/yt/units/unit_object.pyc in _get_unit_data_from_expr(unit_expr, unit_symbol_lut) 407 dimensions = 1 408 for expr in unit_expr.args: --> 409 unit_data = _get_unit_data_from_expr(expr, unit_symbol_lut) 410 cgs_value *= unit_data[0] 411 dimensions *= unit_data[1] /Users/jzuhone/Source/yt-units-notbroke/yt/units/unit_object.pyc in _get_unit_data_from_expr(unit_expr, unit_symbol_lut) 397 398 if isinstance(unit_expr, Pow): --> 399 unit_data = _get_unit_data_from_expr(unit_expr.args[0], unit_symbol_lut) 400 power = unit_expr.args[1] 401 conv = float(unit_data[0]**power) /Users/jzuhone/Source/yt-units-notbroke/yt/units/unit_object.pyc in _get_unit_data_from_expr(unit_expr, unit_symbol_lut) 415 raise UnitParseError("Cannot parse for unit data from '%s'. Please supply" \ 416 " an expression of only Unit, Symbol, Pow, and Mul" \ --> 417 "objects." % str(unit_expr)) 418 419 UnitParseError: Cannot parse for unit data from 'sqrt(cm)'. Please supply an expression of only Unit, Symbol, Pow, and Mulobjects. : UnitParseError: Cannot parse for unit data from 'sqrt(cm)'. Please supply an expression of only Unit, Symbol, Pow, and Mulobjects. [yt.units.unit_object] ``` Responsible: MatthewTurk