Question

所以，我有一个包含国家名称和相应股票指数的字典。要求用户进入五个不同的国家/地区，该程序将获取五个相应的股票指数并对数据执行某些操作。

当被要求输入时，如果可以找到国家，我会检查字典，这会发生五次。现在，处理异常的部分没有按照我的意愿行事。我的循环和/或异常处理有什么问题??

ex_dict = {'United States': '^GSPC','United States of America': '^GSPC', 'Usa': '^GSPC', 'Argentina': '^MERV'} #shortened on purpose

countries = []
print('Please choose five stock exchanges to analyse,' )
print('just name the corresponding countries \n')

for i in range(0, 5):
    while True:
        try:
            countr = input('Please enter country no. %d: ' %(i+1))
            countr = countr.title()            
            if countr in ex_dict.keys():
                print('Found the corresponding stock index! \n')
                countries.append(countr)
            break
        except KeyError:
            print('Country not found, please try again! \n')

Answer 1

此处不会有KeyError因为您的代码永远不会厌烦访问字典，只需检查密钥是否在keys。您可以简单地执行此操作以实现相同的逻辑：

ex_dict = {'United States': '^GSPC','United States of America': '^GSPC', 'Usa': '^GSPC', 'Argentina': '^MERV'} #shortened on purpose

countries = []
print('Please choose five stock exchanges to analyse,' )
print('just name the corresponding countries \n')

for i in range(0, 5):
    while True:
        countr = input('Please enter country no. %d: ' %(i+1))
        countr = countr.title()
        if countr in ex_dict.keys():
            print('Found the corresponding stock index! \n')
            countries.append(countr)
            break
        else:
            print('Country not found, please try again! \n')

示例运行：

Please choose five stock exchanges to analyse,
just name the corresponding countries 

Please enter country no. 1: sdf
Country not found, please try again! 

Please enter country no. 1: USA
Found the corresponding stock index! 

Please enter country no. 2: Aregtng
Country not found, please try again! 

Please enter country no. 2: Argentina
Found the corresponding stock index! 

Please enter country no. 3: United States
Found the corresponding stock index! 

Please enter country no. 4: usa
Found the corresponding stock index! 

Please enter country no. 5: usa
Found the corresponding stock index!

注意：.keys()过度杀戮：要检查某个键是否在字典中，您只需要k in some_dict

Answer 2

你的休息时间不在if范围内......所以它会在第一次尝试时中断。

Answer 3

来自doc

只要请求dict（）对象（使用格式a = adict [key]）并且密钥不在字典中，Python就会引发KeyError。

在您的代码段中，如果您想在用户插入国家/地区字典中不存在的密钥时打印消息，则只需添加else语句而不是catch异常。

您可以通过以下方式更改代码：

if countr in ex_dict.keys():
     print('Found the corresponding stock index! \n')
     countries.append(countr)
     break
else:
    print('Country not found, please try again! \n')

Answer 4

几点：

由于您使用if key in dict.keys()

此外，还有很多循环。我认为for i in range(0,5)已经足够了。不那么复杂。

ex_dict = {'United States': '^GSPC','United States of America': '^GSPC', 'Usa': '^GSPC', 'Argentina': '^MERV'} #shortened on purpose

countries = []
print('Please choose five stock exchanges to analyse,' )
print('just name the corresponding countries \n')

for i in range(0, 5):
    countr = raw_input('Please enter country no. %d: ' %(i+1))
    countr = countr.title()
    if countr in ex_dict.keys():
        print('Found the corresponding stock index! \n')
        countries.append(countr)
    else:
        print('Country not found, please try again! \n')

<强>输出：

C:\Users\dinesh_pundkar\Desktop>python c.py
Please choose five stock exchanges to analyse,
just name the corresponding countries

Please enter country no. 1: USA
Found the corresponding stock index!

Please enter country no. 2: asd
Country not found, please try again!

Please enter country no. 3: asd
Country not found, please try again!

Please enter country no. 4: USA
Found the corresponding stock index!

Please enter country no. 5: United states
Found the corresponding stock index!


C:\Users\dinesh_pundkar\Desktop>

Answer 5

我假设你想要它给你一条消息，如果股票不在字典ex_dict中，我已经修改了代码来做同样的事情。

ex_dict = {'United States': '^GSPC','United States of America': '^GSPC', 'Usa': '^GSPC', 'Argentina': '^MERV'} #shortened on purpose

countries = []
print('Please choose five stock exchanges to analyse,' )
print('just name the corresponding countries \n')

for i in range(0, 5):
    while True:
        try:
            countr = input('Please enter country no. %d: ' %(i+1))
            countr = countr.title()            
            if countr not in ex_dict.keys():
                print ('Try again!')
            else:
                print('Found the corresponding stock index! \n')
                countries.append(countr)

当密钥不在字典中时，如何使用异常处理进行for循环？

5 个答案: