When the length of t does not match the length of observations array, it may couse this error
t = np.linspace(0.5, 54.5, 18)
P = [29.976, 193.96, 362.64, 454.78, 498.42, 517.14, 515.76, 496.38, 472.14, 432.81, 386.95, 352.93, 318.93, 279.47, 260.19, 230.92, 202.67, 180.3, 159.09, 137.31, 120.47, 104.51, 99.371, 89.606, 75.431, 67.137, 58.561, 55.721]
data = Data(t, P)
When the length of t and P are different, program ends with the error “scipy.odr.odrpack.odr_error: number of observations do not match”