Equations and namespaces

Equation parsing

Parsing is done via pyparsing, for now find the grammar at the top of the brian2.equations.equations file.


Each Brian object that saves state variables (e.g. NeuronGroup, Synapses, StateMonitor) has a variables attribute, a dictionary mapping variable names to Variable objects (in fact a Variables object, not a simple dictionary). Variable objects contain information about the variable (name, dtype, units) as well as access to the variable’s value via a get_value method. Some will also allow setting the values via a corresponding set_value method. These objects can therefore act as proxies to the variables’ “contents”.

Variable objects provide the “abstract namespace” corresponding to a chunk of “abstract code”, they are all that is needed to check for syntactic correctness, unit consistency, etc.


The namespace attribute of a group can contain information about the external (variable or function) names used in the equations. It specifies a group-specific namespace used for resolving names in that group. At run time, this namespace is combined with a “run namespace”. This namespace is either explicitly provided to the Network.run method, or the implicit namespace consisting of the locals and globals around the point where the run function is called is used. This namespace is then passed down to all the objects via Network.before_fun which calls all the individual BrianObject.before_run methods with this namespace.