需求场景描述：
购物车程序 ----------- Welcome to BUY_CENTLE ------------ salary：5000 1.iPhone 11 6000 2.mac book 9000 3.coffee 30 4.oython book 80 5.bicycle 1500 ----------------------------------------------- 要求显示： 提示符>>>:1 返回 余额不足，-1000 >>>:5 已加入购物车，当前余额3500 >>>:quit 退出 退出的同时返回： 您已购买以下商品 bicycle 1500 coffee 30 您的余额为:2750 欢迎下次光临！！！
代码实现：
#购物车信息屏显
shop_msg='''
----------- Welcome to BUY_CENTLE ------------
1.iPhone 11 6000
2.mac book 9000
3.coffee 30
4.python book 80
5.bicycle 1500
-----------------------------------------------
'''
print(shop_msg)
#定义购物车列表
shopping_cart=[]
#逻辑代码
user_salary=int(input("Please input your salary : "))
user_choose=input(">>>: ")
while user_choose != 'quit':
if user_choose == '1':
if user_salary < 6000:
print("余额不足",user_salary-6000)
else:
print("已加入购物车，当前余额",user_salary-6000)
user_salary=user_salary-6000
shopping_cart.append('iPhone 11')
elif user_choose == '2':
if user_salary < 9000:
print("余额不足",user_salary-9000)
else:
print("已加入购物车，当前余额",user_salary-9000)
user_salary=user_salary-9000
shopping_cart.append('mac book')
elif user_choose == '3':
if user_salary < 30:
print("余额不足",user_salary-30)
else:
print("已加入购物车，当前余额",user_salary-30)
user_salary=user_salary-30
shopping_cart.append('coffee')
elif user_choose == '4':
if user_salary < 80:
print("余额不足",user_salary-80)
else:
print("已加入购物车，当前余额",user_salary-80)
user_salary=user_salary-80
shopping_cart.append('python book')
elif user_choose == '5':
if user_salary < 1500:
print("余额不足",user_salary-1500)
else:
print("已加入购物车，当前余额",user_salary-1500)
user_salary=user_salary-1500
shopping_cart.append('bicycle')
else:
print("您输入有误，请重新输入！")
user_choose = input(">>>: ")
else:
print('''
---- 您已购买一下商品 ----
''',
shopping_cart,
'''
------ 欢迎下次光临 ------
''')从上面的代码中可以看出，出现大量的重复代码，所以我们使用调用函数，减少代码量，示例：
#!/usr/bin/python
#定义余额判断函数
def yue(user_salary_def,goods_price,goods):
if user_salary_def < goods_price:
print("余额不足", user_salary_def - goods_price)
else:
print("已加入购物车，当前余额", user_salary_def - goods_price)
global user_salary
user_salary = user_salary_def - goods_price
shopping_cart.append(goods)
# 购物车信息屏显
shop_msg = '''
----------- Welcome to BUY_CENTLE ------------
1.iPhone 11 6000
2.mac book 9000
3.coffee 30
4.python book 80
5.bicycle 1500
-----------------------------------------------
'''
print(shop_msg)
# 定义购物车列表
shopping_cart = []
# 逻辑代码
user_salary = int(input("Please input your salary : "))
user_choose = input(">>>: ")
while user_choose != 'quit':
if user_choose == '1':
yue(user_salary,6000,'iPhone 11')
elif user_choose == '2':
yue(user_salary,9000,'mac book')
elif user_choose == '3':
yue(user_salary,30,'coffee')
elif user_choose == '4':
yue(user_salary,80,'python book')
elif user_choose == '5':
yue(user_salary,1500,'bicycle')
else:
print("您输入有误，请重新输入！")
user_choose = input(">>>: ")
else:
print('''
---- 您已购买一下商品 ----
''',
shopping_cart,
'''
------ 下次多买点，小气鬼 ------
''')执行结果示例：
----------- Welcome to BUY_CENTLE ------------
1.iPhone 11 6000
2.mac book 9000
3.coffee 30
4.python book 80
5.bicycle 1500
-----------------------------------------------
Please input your salary : 10000
>>>: 1
已加入购物车，当前余额 4000
>>>: 5
已加入购物车，当前余额 2500
>>>: 4
已加入购物车，当前余额 2420
>>>: quit
---- 您已购买一下商品 ----
['iPhone 11', 'bicycle', 'python book']
------ 下次多买点，小气鬼 ------
Process finished with exit code 0