argv= ['07-leastsq-plot-range-arg.py', '2', '7']
fitting range:  [2.0, 7.0]
header: ['rho(ohm)', 'T(K)']
x: [2.0, 3.0, 4.0, 5.0, 6.0, 7.0]
y: [5.0, 8.0, 15.0, 20.0, 30.0, 50.0]

polynomial fit by scipy.optimize() start:
  lsq result: ai= [13.29999986 -7.13214281  1.73214285]
  y = 13.299999857822812 + -7.132142811356361 * x + 1.7321428541550556 * x^2
