python中函数的局部变量

1、

def discount(price,rate):     ## 定义函数名discount，两个形式参数price和rate
    sell_price = price * rate
    return sell_price        ## 函数返回售价
price = float(input("please input the price:"))    ## 此处接受输入原价
rate = float(input("please input the rate:"))      ## 此处接受输入折扣率
final_price = discount(price,rate)                 ## 调用discount函数，使用位置参数
print("the price after discount is %.2f:" % final_price)    ##  输出最终价格
## 以上函数， price、rate、final_price为全局变量， sell_price为局部变量

please input the price:800
please input the rate:0.6
the price after discount is 480.00:

2、

def discount(price,rate):
    sell_price = price * rate
    return sell_price
price = float(input("please input the price:"))
rate = float(input("please input the rate:"))
final_price = discount(price,rate)
print("the price after discount is %.2f:" % final_price)
print("output sell_price:",sell_price)   ## 此处尝试调用局部变量

please input the price:800
please input the rate:0.6
the price after discount is 480.00:
Traceback (most recent call last):     
  File "D:/programs/python/Lib/idlelib/a.py", line 8, in <module>
    print("output sell_price:",sell_price)
NameError: name 'sell_price' is not defined     ## 不能调用局部变量

3、

def discount(price,rate):
    sell_price = price * rate
    print("please show the price again:", price)
    print("please show the rate again:",rate)
    return sell_price
price = float(input("please input the price:"))
rate = float(input("please input the rate:"))
final_price = discount(price,rate)    ## 在调用discount函数时，调用了全局变量price和rate
print("the price after discount is %.2f:" % final_price)