二分法寻根的Python实现

import math
import matplotlib.pyplot as plt

# RootFinder
EPSILON = float(0.01);

mid_x_list = []
mid_y_list = []

def Bisection(leftX, rightX, func):
    midX = 0.0;
    midY = 0.0;
    i = 0;
    while (rightX - leftX) >= EPSILON:   
        midX = (leftX + rightX) / (2.0 * 100.0) ;
        midY = func(midX);
        mid_x_list.append(midX);
        mid_y_list.append(midY);
        print(i, leftX, rightX, midX, midY);         
        if midY < 0:
            leftX = midX;
        else:
            rightX = midX;            
        i = i + 0.1;        


# MainProgram
# def func(x):
    # return x * x * x - x - 2; # wikipedia
    # return x * x - 2;



#a = 1, b = 2; # wikipedia
a = -50
b = 50;

x_list = []
y_list = []

for i in range(a, b):
    x = i/100.0
    y = math.sin(x);
    x_list.append(x)
    y_list.append(y)

plt.plot(x_list, y_list)

Bisection(a, b, math.sin);

plt.plot(mid_x_list, mid_y_list)

为什么这个实现没有显示正弦波?