scipy.optimize.basinhopping: accept_test returning numpy.bool_ raises an error

[ajkswamy]

Dear Scipy team

When using scipy.optimize.basinhopping, if the accept_test function returns an object of type numpy.bool_, an error occurs. Is this an intentional feature? If not, I think it can be removed allowing accept_test to return numpy.bool_ object.

Thanks
Ajay

[dlax]

Indeed, it seems that this is not handled. According to the code, this function should return an instance of bool or a string with a "special value". And it appears that numpy.bool_ is not an instance of bool. Perhaps this could be better handled without those instance calls.

[andyfaff]

How about:

if testres == 'force_accept':
    ...
elif testres is True:
    ...
else:
    ...

[dlax]

Andrew Nelson wrote:

How about:

|if testres == 'force_accept': ... elif testres is True: ... else: ... |

Not so much better. np.bool_(True) is not True.

As a general rule, a function should return a value of the same type
(i.e. bool here). If you want another behavior, use an exception.