Source code for brian2.groups.subgroup

from brian2.core.base import weakproxy_with_fallback
from brian2.core.spikesource import SpikeSource
from brian2.core.variables import Variables

from .group import Group, Indexing

__all__ = ["Subgroup"]

[docs]class Subgroup(Group, SpikeSource): """ Subgroup of any `Group` Parameters ---------- source : SpikeSource The source object to subgroup. start, stop : int Select only spikes with indices from ``start`` to ``stop-1``. name : str, optional A unique name for the group, or use ``'_subgroup_0'``, etc. """ def __init__(self, source, start, stop, name=None): # A Subgroup should never be constructed from another Subgroup # Instead, use Subgroup(source.source, # start + source.start, stop + source.start) assert not isinstance(source, Subgroup) self.source = weakproxy_with_fallback(source) # Store a reference to the source's equations (if any) self.equations = None if hasattr(self.source, "equations"): self.equations = weakproxy_with_fallback(self.source.equations) if name is None: name = f"{}_subgroup*" # We want to update the spikes attribute after it has been updated # by the parent, we do this in slot 'thresholds' with an order # one higher than the parent order to ensure it takes place after the # parent threshold operation Group.__init__( self, clock=source._clock, when="thresholds", order=source.order + 1, name=name, ) self._N = stop - start self.start = start self.stop = stop = # All the variables have to go via the _sub_idx to refer to the # appropriate values in the source group self.variables = Variables(self, default_index="_sub_idx") # overwrite the meaning of N and i if self.start > 0: self.variables.add_constant("_offset", value=self.start) self.variables.add_reference("_source_i", source, "i") self.variables.add_subexpression( "i", dtype=source.variables["i"].dtype, expr="_source_i - _offset", index="_idx", ) else: # no need to calculate anything if this is a subgroup starting at 0 self.variables.add_reference("i", source) self.variables.add_constant("N", value=self._N) self.variables.add_constant("_source_N", value=len(source)) # add references for all variables in the original group self.variables.add_references(source, list(source.variables.keys())) # Only the variable _sub_idx itself is stored in the subgroup # and needs the normal index for this group self.variables.add_arange( "_sub_idx", size=self._N, start=self.start, index="_idx" ) # special indexing for subgroups self._indices = Indexing(self, self.variables["_sub_idx"]) # Deal with special indices for key, value in self.source.variables.indices.items(): if value == "0": self.variables.indices[key] = "0" elif value == "_idx": continue # nothing to do, already uses _sub_idx correctly else: raise ValueError( f"Do not know how to deal with variable '{key}' " f"using index '{value}' in a subgroup." ) self.namespace = self.source.namespace self.codeobj_class = self.source.codeobj_class self._enable_group_attributes() spikes = property(lambda self: self.source.spikes) def __getitem__(self, item): if not isinstance(item, slice): raise TypeError("Subgroups can only be constructed using slicing syntax") start, stop, step = item.indices(self._N) if step != 1: raise IndexError("Subgroups have to be contiguous") if start >= stop: raise IndexError( f"Illegal start/end values for subgroup, {int(start)}>={int(stop)}" ) return Subgroup(self.source, self.start + start, self.start + stop) def __repr__(self): classname = self.__class__.__name__ return ( f"<{classname} {!r} of {!r} " f"from {self.start} to {self.stop}>" )