# Cannot import brain2modelfitting **URL:** \ **Category:** Support\ **Created:** [4 September 2025 14:50 UTC](https://brian.discourse.group/t/cannot-import-brain2modelfitting/1485 "2025-09-04T14:50:07Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![OttDes](https://avatars.discourse-cdn.com/v4/letter/o/cc9497/32.png) [@OttDes](https://brian.discourse.group/u/OttDes)\ **Post date:** [4 September 2025 14:50 UTC](https://brian.discourse.group/t/cannot-import-brain2modelfitting/1485/1 "2025-09-04T14:50:07Z")
# Description of problem: I am trying to import brian2modelfitting but get and error related to importing NaN # Minimal code to reproduce problem: I install brian2modelfitting: with pip install brian2modelfitting and then import with: from brian2modelfitting import \* # What you have aready tried: I have tried running this on both Google Colab and my own machine. I have also tried changing to an earlier version of numpy, but this gives a different error # Actual output (if relevant) ```auto ImportError Traceback (most recent call last) ``` ```auto /tmp/ipython-input-1516553585.py in () 1 from brian2 import * 2 from brian2tools import * ----> 3 from brian2modelfitting import * 4 from nevergrad.optimization import registry 5 print(sorted(registry.keys())) ``` * * * 2 frames * * * ```auto /usr/local/lib/python3.12/dist-packages/brian2modelfitting/metric.py in 10 from brian2 import Hz, second, Quantity, ms, us, get_dimensions 11 from brian2.units.fundamentalunits import check_units, in_unit, DIMENSIONLESS ---> 12 from numpy import (array, sum, abs, amin, digitize, rint, arange, inf, NaN, 13 clip, mean) 14 ``` ```auto ImportError: cannot import name 'NaN' from 'numpy' (/usr/local/lib/python3.12/dist-packages/numpy/ __init__.py) ``` # Full traceback of error (if relevant) ```auto --------------------------------------------------------------------------- ``` ```auto ImportError Traceback (most recent call last) ``` ```auto /tmp/ipython-input-3395504355.py in () ----> 1 from brian2modelfitting import * ``` * * * 2 frames * * * ```auto /usr/local/lib/python3.12/dist-packages/brian2modelfitting/ __init__.py in 6 7 from .tests import run as run_test ----> 8 from .fitter import * 9 from .optimizer import * 10 from .metric import * ``` ```auto /usr/local/lib/python3.12/dist-packages/brian2modelfitting/fitter.py in 18 from brian2.core.functions import Function 19 from .simulator import RuntimeSimulator, CPPStandaloneSimulator ---> 20 from .metric import Metric, SpikeMetric, TraceMetric, MSEMetric, normalize_weights 21 from .optimizer import Optimizer 22 from .utils import callback_setup, make_dic ``` ```auto /usr/local/lib/python3.12/dist-packages/brian2modelfitting/metric.py in 10 from brian2 import Hz, second, Quantity, ms, us, get_dimensions 11 from brian2.units.fundamentalunits import check_units, in_unit, DIMENSIONLESS ---> 12 from numpy import (array, sum, abs, amin, digitize, rint, arange, inf, NaN, 13 clip, mean) 14 ``` ```auto ImportError: cannot import name 'NaN' from 'numpy' (/usr/local/lib/python3.12/dist-packages/numpy/ __init__.py) ``` ---
**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:** [8 September 2025 11:17 UTC](https://brian.discourse.group/t/cannot-import-brain2modelfitting/1485/2 "2025-09-08T11:17:08Z")
Hi @OttDes I think you are seeing this because the released `brian2wasm` package is not compatible with `numpy 2.x`. When you install it, could you please try with `pip install brian2modelfitting 'numpy<2'`? ---
**Author:** ![OttDes](https://avatars.discourse-cdn.com/v4/letter/o/cc9497/32.png) [@OttDes](https://brian.discourse.group/u/OttDes)\ **Post date:** [9 September 2025 16:20 UTC](https://brian.discourse.group/t/cannot-import-brain2modelfitting/1485/3 "2025-09-09T16:20:29Z")
Hello @mstimberg, Thank you. When I run this I get this error: ```auto --------------------------------------------------------------------------- ``` ```auto ImportError Traceback (most recent call last) ``` ```auto /tmp/ipython-input-3395504355.py in () ----> 1 from brian2modelfitting import * ``` * * * 5 frames * * * ```auto /usr/local/lib/python3.12/dist-packages/nevergrad/optimization/optimizerlib.py in 8 import cma 9 import numpy as np ---> 10 from bayes_opt import UtilityFunction 11 from bayes_opt import BayesianOptimization 12 from ..common.typetools import ArrayLike ``` ```auto ImportError: cannot import name 'UtilityFunction' from 'bayes_opt' (/usr/local/lib/python3.12/dist-packages/bayes_opt/ __init__.py) ``` ---
**Author:** ![OttDes](https://avatars.discourse-cdn.com/v4/letter/o/cc9497/32.png) [@OttDes](https://brian.discourse.group/u/OttDes)\ **Post date:** [9 September 2025 16:29 UTC](https://brian.discourse.group/t/cannot-import-brain2modelfitting/1485/4 "2025-09-09T16:29:34Z")
I have been able to fix that problem. It now seems to be working. Thank you!