The error message says, "array of MATLAB int64 type cannot be returned..." One way to fix this is to return a double array from triarea instead of an int64 array. To do this, make the following change to triarea:
function [a, x] = triarea(b,h)
a(1) = 0.5*(b.* h);
a(2)=1;
a = double(a); % Convert array a to double
Another way to fix this is to call triarea with floats instead of ints. Make the following changes to your Python script:
import matlab.engine
eng = matlab.engine.start_matlab()
b = float(input("dimmi la base: ")) # convert input to float instead of int
h = float(input("dimmi l'altezza: ")) # convert input to float instead of int
while b < 0:
print("\ni dati inseriti non sono validi\n")
b = float(input("dimmi la base: ")) # convert input to float instead of int
while h < 0:
print("\ni dati inseriti non sono validi\n")
h = float(input("dimmi l'altezza: ")) # convert input to float instead of int
res = eng.triarea(b, h)
print("l'area del triangolo è", res[0])
