I am post processing some MHD simulations done with FLASH using yt (yt version 4.3.0). Initially, the simulation has no particles, but over time, we add some (sink) particles to it. I would like to use the boolean ds.particles_exist to check if a given FLASH HDF5 particle file has any particles in it or not. It works fine when there are particles, but gives a key error when there are no particles, instead of returning False. The same issue also occurs with an earlier version of yt (4.0.4). Traceback below: In [1]: yt.__version__ Out[1]: '4.3.0' In [4]: ds=yt.load('FLASH_part_0050') yt : [INFO ] 2023-10-24 11:01:22,508 Parameters: current_time = 50966272658115.96 yt : [INFO ] 2023-10-24 11:01:22,508 Parameters: domain_dimensions = [1 1 1] yt : [INFO ] 2023-10-24 11:01:22,508 Parameters: domain_left_edge = [-3.703e+18 -3.703e+18 -3.703e+18] yt : [INFO ] 2023-10-24 11:01:22,508 Parameters: domain_right_edge = [3.703e+18 3.703e+18 3.703e+18] yt : [INFO ] 2023-10-24 11:01:22,509 Parameters: cosmological_simulation = 0 In [5]: ds.particles_exist yt : [INFO ] 2023-10-24 11:01:26,270 Allocating for 3 particles Out[5]: True In [6]: ds=yt.load('FLASH_part_0000') yt : [INFO ] 2023-10-24 11:01:41,713 Parameters: current_time = 0.0 yt : [INFO ] 2023-10-24 11:01:41,713 Parameters: domain_dimensions = [1 1 1] yt : [INFO ] 2023-10-24 11:01:41,714 Parameters: domain_left_edge = [-3.703e+18 -3.703e+18 -3.703e+18] yt : [INFO ] 2023-10-24 11:01:41,714 Parameters: domain_right_edge = [3.703e+18 3.703e+18 3.703e+18] yt : [INFO ] 2023-10-24 11:01:41,714 Parameters: cosmological_simulation = 0 In [7]: ds.particles_exist --------------------------------------------------------------------------- KeyError Traceback (most recent call last) Input In [7], in <cell line: 1>() ----> 1 ds.particles_exist File ~/.local/lib/python3.9/site-packages/yt/data_objects/static_output.py:1238, in Dataset.particles_exist(self) 1236 @property 1237 def particles_exist(self): -> 1238 for pt, f in itertools.product(self.particle_types_raw, self.field_list): 1239 if pt == f[0]: 1240 return True File ~/.local/lib/python3.9/site-packages/yt/data_objects/static_output.py:657, in Dataset.field_list(self) 655 @property 656 def field_list(self): --> 657 return self.index.field_list File ~/.local/lib/python3.9/site-packages/yt/data_objects/static_output.py:606, in Dataset.index(self) 603 @property 604 def index(self): 605 if self._instantiated_index is None: --> 606 self._instantiated_index = self._index_class( 607 self, dataset_type=self.dataset_type 608 ) 609 # Now we do things that we need an instantiated index for 610 # ...first off, we create our field_info now. 611 oldsettings = np.geterr() File ~/.local/lib/python3.9/site-packages/yt/geometry/particle_geometry_handler.py:72, in ParticleIndex.__init__(self, ds, dataset_type) 70 self.dataset = weakref.proxy(ds) 71 self.float_type = np.float64 ---> 72 super().__init__(ds, dataset_type) 73 self._initialize_index() File ~/.local/lib/python3.9/site-packages/yt/geometry/geometry_handler.py:42, in Index.__init__(self, ds, dataset_type) 39 self._setup_geometry() 41 mylog.debug("Initializing data grid data IO") ---> 42 self._setup_data_io() 44 # Note that this falls under the "geometry" object since it's 45 # potentially quite expensive, and should be done with the indexing. 46 mylog.debug("Detecting fields.") File ~/.local/lib/python3.9/site-packages/yt/geometry/geometry_handler.py:124, in Index._setup_data_io(self) 122 if getattr(self, "io", None) is not None: 123 return --> 124 self.io = io_registry[self.dataset_type](self.dataset) File ~/.local/lib/python3.9/site-packages/yt/frontends/flash/io.py:224, in IOHandlerFLASHParticle.__init__(self, ds) 222 self._handle = ds._handle 223 self._particle_fields = determine_particle_fields(self._handle) --> 224 self._position_fields = [ 225 self._particle_fields[f"particle_pos{ax}"] for ax in "xyz" 226 ] File ~/.local/lib/python3.9/site-packages/yt/frontends/flash/io.py:225, in <listcomp>(.0) 222 self._handle = ds._handle 223 self._particle_fields = determine_particle_fields(self._handle) 224 self._position_fields = [ --> 225 self._particle_fields[f"particle_pos{ax}"] for ax in "xyz" 226 ] KeyError: 'particle_posx'