Python 函数绘图及函数图像微分与积分

# Python 3.ximport turtlefrom random import *from math import *from time import *def draw():  turtle.pencolor(random(), random(), random())  global n, sf  n = 0  sf = 0  while n > width / (-2 * zoom):    f = evale(express, n)    drawf(n, f)    n -= (1 / zoom)  n = 0  sf = 0  while n < width / (2 * zoom):    f = evale(express, n)    drawf(n, f)    n += (1 / zoom)def drawf(n, f):  if n == 0 or isnan(f.real):    turtle.penup()  else:    turtle.pendown()  if isnan(f.real):    f = 0  elif n.imag != 0:    f = abs(f)  if hight / -zoom < f.real < hight / zoom:    turtle.goto(n * zoom, f.real * zoom)def drawxy():  turtle.clear()  turtle.pencolor(0, 0, 0)  turtle.penup()  turtle.goto(0, 0)  turtle.pendown()  turtle.goto(width / -2, 0)  turtle.goto(width / 2, 0)  turtle.goto(0, 0)  turtle.goto(0, hight / 2)  turtle.goto(0, hight / -2)def format(s):  s = s.replace("^","**")  s = s.replace("@","differentiate")  s = s.replace("$","integral")  return sdef evale(s, n):  x = n  try:    return eval(s)  except BaseException:    return nandef differentiate(s):  dx = 0.1 / zoom  f1 = evale(s, n)  df = evale(s, n + dx) - f1  return df / dxdef integral(s):  global sf  dx = copysign(1 / zoom, n)  f1 = evale(s, n)  df = (f1 + evale(s, n + dx)) / 2  sf = sf + df * dx  return sfdef rezoom(n):  global zoom  zoom = n  drawxy()  draw()zoom = eval(input("zoom = "))width = 1280hight = 720turtle.setup(width, hight)turtle.hideturtle()turtle.delay(0)turtle.pensize(2)drawxy()while True:  express = format(input("f(x) = "))  draw()  while True:    i = input(": ")    if i == "break":      break    else:      try:        print(eval(i))      except BaseException:        print("Input error.")