Python查找函数f（x）=0的根，python,''' root = r

Python查找函数f（x）=0的根，python,''' root = r

''' root = ridder(f,a,b,tol=1.0e-9).    Finds a root of f(x) = 0 with Ridder's method.    The root must be bracketed in (a,b).'''import errorfrom math import sqrtdef ridder(f,a,b,tol=1.0e-9):       fa = f(a)    if fa == 0.0: return a    fb = f(b)    if fb == 0.0: return b    if fa*fb > 0.0: error.err('Root is not bracketed')    for i in range(30):      # Compute the improved root x from Ridder's formula        c = 0.5*(a + b); fc = f(c)        s = sqrt(fc**2 - fa*fb)        if s == 0.0: return None        dx = (c - a)*fc/s        if (fa - fb) < 0.0: dx = -dx        x = c + dx; fx = f(x)      # Test for convergence        if i > 0:            if abs(x - xOld) < tol*max(abs(x),1.0): return x        xOld = x      # Re-bracket the root as tightly as possible        if fc*fx > 0.0:            if fa*fx < 0.0: b = x; fb = fx            else:           a = x; fa = fx        else:            a = c; b = x; fa = fc; fb = fx    return None    print 'Too many iterations'