Python implements the reciprocal calculation method, and python implements reciprocal calculation.

Python implements the reciprocal calculation method, and python implements reciprocal calculation.

This example describes how to calculate the countdown in python. Share it with you for your reference. The details are as follows:

class Expr:  def __add__(self, other):   return Plus(self, other)  def __mul__(self, other):   return Times(self, other) class Int(Expr):  def __init__(self, n):   self.n = n  def d(self, v):   return Int(0)  def __str__(self):   return `self.n` class Var(Expr):  def __init__(self, var):   self.var = var  def d(self, v):   return Int(self.var == v and 1 or 0)  def __str__(self):   return self.var class Plus(Expr):  def __init__(self, a, b):   self.e1 = a   self.e2 = b  def d(self, v):   return Plus(self.e1.d(v), self.e2.d(v))  def __str__(self):   return "(%s + %s)" % (self.e1, self.e2) class Times(Expr):  def __init__(self, a, b):   self.e1 = a   self.e2 = b  def d(self, v):   return Plus(Times(self.e1, self.e2.d(v)), Times(self.e1.d(v), self.e2)) def __str__(self):   return "(%s * %s)" % (self.e1, self.e2) if __name__ == "__main__":  x = Var("x")  a = Var("a")  b = Var("b")  c = Var("c")  e = a * x * x + b * x + c  print "d(%s, x) = %s" % (e, e.d("x")) 

I hope this article will help you with Python programming.