Variables class

(Shortest import: from brian2.core.variables import Variables)

class brian2.core.variables.Variables(owner, default_index='_idx')

Bases: collections.abc.Mapping

A container class for storing Variable objects. Instances of this class are used as the Group.variables attribute and can be accessed as (read-only) dictionaries.

Parameters

owner : Nameable

The object (typically a Group) “owning” the variables.

default_index : str, optional

The index to use for the variables (only relevant for ArrayVariable and DynamicArrayVariable). Defaults to '_idx'.

Attributes

indices	A dictionary given the index name for every array name
owner	A reference to the Group owning these variables

Methods

add_arange(name, size[, start, dtype, ...])	Add an array, initialized with a range of integers.
add_array(name, size[, dimensions, values, ...])	Add an array (initialized with zeros).
add_arrays(names, size[, dimensions, dtype, ...])	Adds several arrays (initialized with zeros) with the same attributes (size, units, etc.).
add_auxiliary_variable(name[, dimensions, ...])	Add an auxiliary variable (most likely one that is added automatically to abstract code, e.g.
add_constant(name, value[, dimensions])	Add a scalar constant (e.g.
add_dynamic_array(name, size[, dimensions, ...])	Add a dynamic array.
add_object(name, obj)	Add an arbitrary Python object.
add_reference(name, group[, varname, index])	Add a reference to a variable defined somewhere else (possibly under a different name).
add_references(group, varnames[, index])	Add all Variable objects from a name to Variable mapping with the same name as in the original mapping.
add_referred_subexpression(name, group, ...)
add_subexpression(name, expr[, dimensions, ...])	Add a named subexpression.
create_clock_variables(clock[, prefix])	Convenience function to add the t and dt attributes of a clock.

Details

indices

A dictionary given the index name for every array name

owner

A reference to the Group owning these variables

add_arange(name, size, start=0, dtype=<class 'numpy.int32'>, constant=True, read_only=True, unique=True, index=None)

Add an array, initialized with a range of integers.

Parameters

name : str

The name of the variable.

size : int

The size of the array.

start : int

The start value of the range.

dtype : dtype, optional

The dtype used for storing the variable. If none is given, defaults to np.int32.

constant : bool, optional

Whether the variable’s value is constant during a run. Defaults to True.

read_only : bool, optional

Whether this is a read-only variable, i.e. a variable that is set internally and cannot be changed by the user. Defaults to True.

index : str, optional

The index to use for this variable. Defaults to Variables.default_index.

unique : bool, optional

See ArrayVariable. Defaults to True here.

add_array(name, size, dimensions=Dimension(), values=None, dtype=None, constant=False, read_only=False, scalar=False, unique=False, index=None)

Add an array (initialized with zeros).

Parameters

name : str

The name of the variable.

dimensions : Dimension, optional

The physical dimensions of the variable.

size : int

The size of the array.

values : ndarray, optional

The values to initalize the array with. If not specified, the array is initialized to zero.

dtype : dtype, optional

The dtype used for storing the variable. If none is given, defaults to core.default_float_dtype.

constant : bool, optional

Whether the variable’s value is constant during a run. Defaults to False.

scalar : bool, optional

Whether this is a scalar variable. Defaults to False, if set to True, also implies that size() equals 1.

read_only : bool, optional

Whether this is a read-only variable, i.e. a variable that is set internally and cannot be changed by the user. Defaults to False.

index : str, optional

The index to use for this variable. Defaults to Variables.default_index.

unique : bool, optional

See ArrayVariable. Defaults to False.

add_arrays(names, size, dimensions=Dimension(), dtype=None, constant=False, read_only=False, scalar=False, unique=False, index=None)

Adds several arrays (initialized with zeros) with the same attributes (size, units, etc.).

Parameters

names : list of str

The names of the variable.

dimensions : Dimension, optional

The physical dimensions of the variable.

size : int

The sizes of the arrays.

dtype : dtype, optional

The dtype used for storing the variables. If none is given, defaults to core.default_float_dtype.

constant : bool, optional

Whether the variables’ values are constant during a run. Defaults to False.

scalar : bool, optional

Whether these are scalar variables. Defaults to False, if set to True, also implies that size() equals 1.

read_only : bool, optional

Whether these are read-only variables, i.e. variables that are set internally and cannot be changed by the user. Defaults to False.

index : str, optional

The index to use for these variables. Defaults to Variables.default_index.

unique : bool, optional

See ArrayVariable. Defaults to False.

add_auxiliary_variable(name, dimensions=Dimension(), dtype=None, scalar=False)

Add an auxiliary variable (most likely one that is added automatically to abstract code, e.g. _cond for a threshold condition), specifying its type and unit for code generation.

Parameters

name : str

The name of the variable

dimensions : Dimension

The physical dimensions of the variable.

dtype : dtype, optional

The dtype used for storing the variable. If none is given, defaults to core.default_float_dtype.

scalar : bool, optional

Whether the variable is a scalar value (True) or vector-valued, e.g. defined for every neuron (False). Defaults to False.

add_constant(name, value, dimensions=Dimension())

Add a scalar constant (e.g. the number of neurons N).

Parameters

name : str

The name of the variable

value: reference to the variable value :

The value of the constant.

dimensions : Dimension, optional

The physical dimensions of the variable. Note that the variable itself (as referenced by value) should never have units attached.

add_dynamic_array(name, size, dimensions=Dimension(), values=None, dtype=None, constant=False, needs_reference_update=False, resize_along_first=False, read_only=False, unique=False, scalar=False, index=None)

Add a dynamic array.

Parameters

name : str

The name of the variable.

dimensions : Dimension, optional

The physical dimensions of the variable.

size : int or tuple of int

The (initital) size of the array.

values : ndarray, optional

The values to initalize the array with. If not specified, the array is initialized to zero.

dtype : dtype, optional

The dtype used for storing the variable. If none is given, defaults to core.default_float_dtype.

constant : bool, optional

Whether the variable’s value is constant during a run. Defaults to False.

needs_reference_update : bool, optional

Whether the code objects need a new reference to the underlying data at every time step. This should be set if the size of the array can be changed by other code objects. Defaults to False.

scalar : bool, optional

Whether this is a scalar variable. Defaults to False, if set to True, also implies that size() equals 1.

read_only : bool, optional

Whether this is a read-only variable, i.e. a variable that is set internally and cannot be changed by the user. Defaults to False.

index : str, optional

The index to use for this variable. Defaults to Variables.default_index.

unique : bool, optional

See DynamicArrayVariable. Defaults to False.

add_object(name, obj)

Add an arbitrary Python object. This is only meant for internal use and therefore only names starting with an underscore are allowed.

Parameters

name : str

The name used for this object (has to start with an underscore).

obj : object

An arbitrary Python object that needs to be accessed directly from a CodeObject.

add_reference(name, group, varname=None, index=None)

Add a reference to a variable defined somewhere else (possibly under a different name). This is for example used in Subgroup and Synapses to refer to variables in the respective NeuronGroup.

Parameters

name : str

The name of the variable (in this group, possibly a different name from var.name).

group : Group

The group from which var() is referenced

varname : str, optional

The variable to refer to. If not given, defaults to name.

index : str, optional

The index that should be used for this variable (defaults to Variables.default_index).

add_references(group, varnames, index=None)

Add all Variable objects from a name to Variable mapping with the same name as in the original mapping.

Parameters

group : Group

The group from which the variables are referenced

varnames : iterable of str

The variables that should be referred to in the current group

index : str, optional

The index to use for all the variables (defaults to Variables.default_index)

add_referred_subexpression(name, group, subexpr, index)

add_subexpression(name, expr, dimensions=Dimension(), dtype=None, scalar=False, index=None)

Add a named subexpression.

Parameters

name : str

The name of the subexpression.

dimensions : Dimension

The physical dimensions of the subexpression.

expr : str

The subexpression itself.

dtype : dtype, optional

The dtype used for the expression. Defaults to core.default_float_dtype.

scalar : bool, optional

Whether this is an expression only referring to scalar variables. Defaults to False

index : str, optional

The index to use for this variable. Defaults to Variables.default_index.

create_clock_variables(clock, prefix='')

Convenience function to add the t and dt attributes of a clock.

Parameters

clock : Clock

The clock that should be used for t and dt.

prefix : str, optional

A prefix for the variable names. Used for example in monitors to not confuse the dynamic array of recorded times with the current time in the recorded group.