Python字典值修改后循环重复时未生效的技术问题

你这段代码的问题很明确：每次循环都会重新创建airplane_ticket字典。把字典定义放在while True循环里面，意味着每轮循环开始时，available都会被重置为初始值5，上一轮修改的结果自然留不住。

把字典的初始化代码移到循环外面，这样整个循环过程中字典只会被创建一次，修改后的剩余票数会被持续保留：

# 字典初始化放在循环外，只执行一次
airplane_ticket = {'Berlin':'','price':'$700', 'available':5}   
while True:    
    print(airplane_ticket)  
    name_ticket = input('please enter the name of city you want to reserved its ticket: ')  
    if name_ticket == 'Berlin':
        number = int(input('How many ticket you need: '))    
        airplane_ticket['available'] -= number

如果想避免用户购买负数或者超过剩余数量的票，可以加个简单的判断逻辑：

airplane_ticket = {'Berlin':'','price':'$700', 'available':5}   
while True:    
    print(airplane_ticket)  
    name_ticket = input('please enter the name of city you want to reserved its ticket: ')  
    if name_ticket == 'Berlin':
        number = int(input('How many ticket you need: '))  
        if 0 < number <= airplane_ticket['available']:
            airplane_ticket['available'] -= number
            print(f"Successfully booked {number} tickets!")
        else:
            print(f"Invalid number! Only {airplane_ticket['available']} tickets left.")

内容的提问来源于stack exchange，提问作者hosein moradi.k