python如何计算面积？

#!/usr/bin/python
#-*-coding:utf-8 -*-
name = raw_input("Please input your name here : ")
if name == '':
    print("we don't like anonymous")
else:
    choose = input("Which shape would you like to choose 1:Rectangle, 2:Square, 3:Triangle or 4 Round? :")
    if choose == 1:
        width, height = map(int, raw_input("Input width and height here, like 5 8 :").split())
        print( "Area = %d" % (width * height))
    elif choose == 2:
        length = input("Input width and height here, like 4:")
        print( "Area = %d" % length ** 2)
    elif choose == 3:
        width, height = map(int, raw_input("Input width and height here, like 5 8 :").split())
        print( "Area = %d" % (width * height / 2))
    elif choose == 4:
        diameter = input("Input diameter here like 3 :")
        print ("Area = %.2f" % (3.14 * (diameter / 2) ** 2))
    else:
        print( "Invalid choose")