scipy leastsq sample.

leastsq.py

#!/usr/bin/env python

import numpy as np
from scipy.optimize import leastsq


def fit_func(parameter, x, y):
	a = parameter[0]
	b = parameter[1]
	residual = y - (a*x*x + b)
	return residual


px = [-5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5]
py = [25.5, 16.9, 9.7, 4.3, 2.1, 1.02, 1.98, 4.9, 9.9, 15.8, 25.7]

px = np.array(px)
py = np.array(py)

parameter0 = np.array([0, 0])

result = leastsq(fit_func, parameter0, args=(px, py))

print result[0]