python - 为什么我的 python 代码运行了两次？

Question

每当我为“你想求另一个形状的面积吗？”输入“否”时它再次问我这个问题。这是我的代码:-

def calculate_area():
  print "Welcome to the area calculator"
  user= raw_input("Enter the shape you would like to calculate the area of:").lower()

  def restart():
    answer= raw_input( "Would you like to find the area of another shape?('yes' or 'no')")
    if answer=="yes":
      calculate_area()
  def rerun():
    restart()


  if user== "rectangle":
    def calculate_rectangle():
      rect1= int(raw_input("Enter the length of the first side:"))
      rect2= int(raw_input("Enter the length of the second side:"))
      print "The area is:",float(rect1*rect2)
    calculate_rectangle()
    rerun()

  elif user== "square":
    def calculate_square():
      square=int(raw_input("Enter the length of the side:"))
      print "The area is:",float(square**2)
    calculate_square()
    rerun()


  elif user== "triangle":
    def calculate_triangle():
      triangle=int(raw_input("Enter the length of the base:"))
      triangle2=int(raw_input("Enter the height of the triangle:"))
      print "The area is:", float((0.5*triangle)*triangle2)
    calculate_triangle()
    rerun()


  elif user== "trapezoid":
    def calculate_trap():
      trapezoid=int(raw_input("Enter the length of base 1:"))
      trapezoid2=int(raw_input("Enter the length of base 2:"))
      trapezoid3=int(raw_input("Enter the height:"))
      print "The area is:", (float(trapezoid+trapezoid2)/2*float(trapezoid3))
    calculate_trap()
    rerun()

  elif user== "circle":
    def calculate_circle():
      circle=int(raw_input("Enter the radius:"))
      print "The area is:", (float((circle**2)*3.14))
    calculate_circle()
    rerun()

  elif user== "rhombus":
    def calculate_rhombus():
      rhombus1=int(raw_input("Enter the length of diagonal 1:"))
      rhombus2=int(raw_input("Enter the length of diagonal 2:"))
      print "The area is:", (float((rhombus1*rhombus2)/2))
    calculate_rhombus()
    rerun()    

  else:
    print "Shape not recognized"
  rerun()

此代码位于“def restart”下，每当我键入“no”时运行两次。为什么会这样？

Answer 1

您为每个问题调用两次 rerun():

if user== "rectangle":
    # ...
    rerun()

elif user== "square":
    # ...
    rerun()

# all other elif branches each have rerun()

else:
    print "Shape not recognized"
rerun()

你在这里依赖递归，但是递归函数return;当您输入 "No" 时，restart() 返回到 rerun()，它将控制权返回到它被调用的位置，所以在您的 if ... elif ... 分支之一。在这些分支之后您再次调用rerun()。

您一开始就不应该使用递归。改为使用无限循环:

print "Welcome to the area calculator"

while True:
    user = raw_input("Enter the shape you would like to calculate the area of:").lower()
    # execute their choice
    if user== "rectangle":
        # ...
    # etc.

    else:
        print "Shape not recognized"

    answer = raw_input( "Would you like to find the area of another shape?('yes' or 'no')")
    if answer != "yes":
        break

末尾的 break 结束了 while True 循环。如果输入 yes，则 while 循环从顶部继续，重新运行整个 block 。