# About the Custom Events **URL:** \ **Category:** Support\ **Created:** [6 January 2022 10:30 UTC](https://brian.discourse.group/t/about-the-custom-events/574 "2022-01-06T10:30:34Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![SEU\_diff](https://yyz2.discourse-cdn.com/free1/user_avatar/brian.discourse.group/seu_diff/32/245_2.png) [@SEU\_diff](https://brian.discourse.group/u/SEU_diff)\ **Post date:** [6 January 2022 10:30 UTC](https://brian.discourse.group/t/about-the-custom-events/574/1 "2022-01-06T10:30:34Z")
# Description of problem I’m doing some work with the Tempotron rule. ![image](https://global.discourse-cdn.com/free1/uploads/brian/original/1X/94eef4fd38481885f32abf62998e85858102aafc.png) And I use the Custom events to do this. But there’re Errors occured. # Minimal code to reproduce problem ```auto # parameters v_th = 1 # -54 * mV v_reset = 0 # -65 * mV tau_m = 350 * ms N_spike = 2*34*34 N_Tempotron = 10 duration = 350 * ms t_refractory = 5 * ms defaultclock.dt = 0.001*ms lr = 0.001 # eqs lif_model = ''' dv/dt = (v_reset - v)/tau_m : 1 dtrace/dt = -trace/tau_m : 1 fired_status : boolean label : 1 ''' T_pre_eq = ''' v += w trace += 1 ''' T_post_eq = ''' fired_status = True ''' Tempotron_ftf_eq = ''' w += lr * trace ''' Tempotron_fw_eq = ''' w -= lr * trace trace = 0 fired_status = False ''' # load data train_index, train_timestamp, test_index, test_timestamp = load_data() train_label, test_label = load_label() # input group input_group = SpikeGeneratorGroup(N_spike, train_index[0],train_timestamp[0]*ms, sorted=True) # Tempotron Group Tempotron_group = NeuronGroup(N_Tempotron, model=lif_model,threshold='v > v_th',reset='v=v_reset', refractory=t_refractory, method='exact', events={'fail_to_fire': '(not fired_status) and (label == i) and (t%duration==0) ', 'fire_wrongly': 'fired_status and (label != i)'}) Tempotron_group.v = v_reset Tempotron_group.fired_status = False # synapse i2T_synapes = Synapses(input_group, Tempotron_group, model='w : 1', on_pre=T_pre_eq, on_post={'post': T_post_eq, 'Tempotron_ftf': Tempotron_ftf_eq, 'Tempotron_fw': Tempotron_fw_eq}, on_event={'Tempotron_ftf': 'fail_to_fire', 'Tempotron_fw': 'fire_wrongly'}) i2T_synapes.connect() i2T_synapes.w = 'rand() * 0.001' # monitor T_mon = SpikeMonitor(Tempotron_group) # run for item in tqdm(range(len(train_index))): Tempotron_group.label = train_label[item] if item == 0: run(0*ms) run(duration) else: input_group.set_spikes(indices=train_index[item], times=train_timestamp[item]*ms+item*duration, sorted=True) run(duration) Tempotron_group.fired_status = False ``` # What you have aready tried I’ve read the Custom events document, but didn’t found the reason. Is there anything I miss? # Full traceback of error (if relevant) Traceback (most recent call last): File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\brian2\core\network.py”, line 892, in before\_run obj.before\_run(run\_namespace) File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\brian2\groups\group.py”, line 1135, in before\_run self.create\_code\_objects(run\_namespace) File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\brian2\groups\group.py”, line 1128, in create\_code\_objects code\_object = self.create\_default\_code\_object(run\_namespace) File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\brian2\groups\group.py”, line 1100, in create\_default\_code\_object self.update\_abstract\_code(run\_namespace=run\_namespace) File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\brian2\groups\neurongroup.py”, line 249, in update\_abstract\_code stateupdate\_output = StateUpdateMethod.apply\_stateupdater(self.group.equations, File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\brian2\utils\caching.py”, line 101, in cached\_func func.\_cache[cache\_key] = func(\*args, \*\*kwds) File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\brian2\stateupdaters\base.py”, line 222, in apply\_stateupdater code = stateupdater(equations, variables, method\_options) File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\brian2\stateupdaters\exact.py”, line 226, in **call** rhs = rhs.subs(\_S[row\_idx, 0], varname) File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\sympy\core\basic.py”, line 948, in subs rv = rv.\_subs(old, new, \*\*kwargs) File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\sympy\core\cache.py”, line 72, in wrapper retval = cfunc(\*args, \*\*kwargs) File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\sympy\core\basic.py”, line 1062, in \_subs rv = fallback(self, old, new) File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\sympy\core\basic.py”, line 1039, in fallback rv = self.func(\*args) File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\sympy\core\cache.py”, line 72, in wrapper retval = cfunc(\*args, \*\*kwargs) File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\sympy\core\operations.py”, line 53, in **new** args = list(map(_sympify_, args)) File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\sympy\core\sympify.py”, line 513, in \_sympify return sympify(a, strict=True) File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\sympy\core\sympify.py”, line 434, in sympify raise SympifyError(a) sympy.core.sympify.SympifyError: SympifyError: \ The above exception was the direct cause of the following exception: Traceback (most recent call last): File “C:\ProgramData\Anaconda3\envs\python38\lib\site-packages\brian2\core\network.py”, line 894, in before\_run raise BrianObjectException(“An error occurred when preparing an object.”, obj) from ex brian2.core.base.BrianObjectException: Error encountered with object named ‘neurongroup\_stateupdater’. Object was created here (most recent call only, full details in debug log): File ‘C:/Dev/Python/LogicFunction/Application/clf\_N-MNIST/clf\_NMNIST\_test.py’, line 68, in Tempotron\_group = NeuronGroup(N\_Tempotron, model=lif\_model,threshold=‘v \> v\_th’,reset=‘v=v\_reset’, An error occurred when preparing an object. (See above for original error message and traceback.) ---
**Author:** ![mstimberg](https://yyz2.discourse-cdn.com/free1/user_avatar/brian.discourse.group/mstimberg/32/11_2.png) [@mstimberg](https://brian.discourse.group/u/mstimberg)\ **Post date:** [6 January 2022 16:11 UTC](https://brian.discourse.group/t/about-the-custom-events/574/2 "2022-01-06T16:11:22Z")
Hi @SEU_diff . It seems you came across a bug… We are using [sympy](https://sympy.org) for symbolic processing of the equations, and this fails here because it confuses your variable `trace` with a function of the same name (the trace of a matrix, I guess). You could work around this specific problem by renaming your `trace` variable to something else. ---
**Author:** ![SEU\_diff](https://yyz2.discourse-cdn.com/free1/user_avatar/brian.discourse.group/seu_diff/32/245_2.png) [@SEU\_diff](https://brian.discourse.group/u/SEU_diff)\ **Post date:** [10 January 2022 16:53 UTC](https://brian.discourse.group/t/about-the-custom-events/574/3 "2022-01-10T16:53:10Z")
Thank you very much! I fix it by changing the variable name.😊