cannot import scipy.optimize.Bounds

[larkypython]

I wrote a very simple program to test the optimize of scipy, it all works for unconstrained optimizations, but when it comes to constrained optimization, the Bounds, LinearConstraint module will be needed, but I cannot import any of them. the program is as shown below:

from scipy import optimize
# from scipy.optimize import minimize
# from scipy.optimize import Bounds
# from scipy.optimize import LinearConstraint
import numpy

def f(x):
	return 0.5*(1-x[0])**2+(x[1]-x[0]**2)**2

bounds = Bounds([0, -0.5], [1.0, 2.0])

result=optimize.minimize(f, [0.5, -0.5], method='BFGS', bounds=bounds)
print(result.x)

the error says:

File "testopt.py", line 13, in <module>
    bounds = Bounds([0, -0.5], [1.0, 2.0])
NameError: name 'Bounds' is not defined

I also tried to import them one by one:

from scipy.optimize import minimize
from scipy.optimize import Bounds
from scipy.optimize import LinearConstraint

but, the error becomes:

Traceback (most recent call last):
  File "testopt.py", line 3, in <module>
    from scipy.optimize import Bounds
ImportError: cannot import name 'Bounds'

so no matter what, Bounds and LinearConstraint will never be found. I am wondering what kind of problem will this be, if the installation got problems, the minimize function should not work either.

Please help out, this already hindered me for weeks.