python 3.2 调用自定义函数,输入三条边,判断是否能组成三角形

下述脚本是个简单的脚本，是学习python 3.2函数时编写的。拿出来，希望大家提些建议，以便改进。

#-*- encoding: utf-8 -*-
'''
Created on 2011-7-26
Modified on 2011-7-27
Debug on 2011-7-28

@author: songwenjun
'''

def istrigon(x,y,z):
    if (x == 0) or (y == 0) or (z == 0):
        print("The game is over")
        exit()

    if x < 0 :
        x = input("The number of side inefficacy,so enter the first of side again, please:")
        x = float(x)

    if y < 0 :
        y = input("The number of side inefficacy,so enter the second of side again, please:")
        y = float(y)       
   
    if z < 0 :
        z = input("The number of side inefficacy,so enter the third of side again, please:")
        z = float(z)
   
    if (x >= (y + z)) or (y >= (x + z)) or (z >= (x + y)):
        return False

    if (x <= (abs(y - z))) or (y <= (abs(x - z))) or (z <= (abs(x - y))):
        return False
   
    return True

iswhile = True

print("The game is order to checking three sides for trigon")

while iswhile :
    print("Enter three number for side of trigon please:")
    a = input("Enter the first of side, please:")
    a = float(a)
 
    b = input("Enter the seconde of side, please:")
    b = float(b)

    c = input("Enter the third of side, please:")
    c = float(c)
    
    if istrigon(a,b,c) :
        print("it's ok!")
    else :
        print("Sorry,it isn't trigon")

    isgoon = input("Do you want to go on? 1 is again; 0 is exit programme:")
    isgoon = int(isgoon)

    if isgoon == 1 :
        continue
    else :
        iswhile = False

print("Done1")