[英]How to raise custom dictionary KeyError message
I'm writing some scripts that will be used by non-python users. 我正在编写一些将由非python用户使用的脚本。 I have a Config class that has dictionaries and I'd like to be able to raise a custom exception for KeyError. 我有一个包含字典的Config类,我希望能够为KeyError引发一个自定义异常。 Is there an elegant way to do this other than writing a method that raises an exception when checking for the value in the dictionary? 除了编写一个在检查字典中的值时引发异常的方法之外,还有一种优雅的方法吗?
Here's an example: 这是一个例子:
class ConfigError(Exception): pass
class Config:
def __init__(self):
self.cars = {'BMW': 'M5', 'Honda': 'Civic'}
def get_car(self, name):
try:
return self.cars[name]
except KeyError, e:
raise ConfigError("Car %s doesn't exist!!!" % name)
conf = Config()
print 'Car: %s' % conf.cars['BMW']
print 'Car: %s' % conf.cars['Mercedes']
Here's the output: 这是输出:
Car: M5
Traceback (most recent call last):
File "test.py", line 17, in ?
print 'Car: %s ' % conf.cars['Mercedes']
KeyError: 'Mercedes'
I know I can write a method like Config.get_car() above and raise a custom exception, but I'd like to be able to raise the custom exception when directly trying to access the Config.cars dictionary. 我知道我可以编写一个像上面的Config.get_car()这样的方法并引发一个自定义异常,但我希望能够在直接尝试访问Config.cars字典时引发自定义异常。 I'd like to do so because there's actually more dictionaries in the config, but I only need to raise a custom exception for one of the dictionaries and would like to keep how the data is access consistent (all as dictionaries). 我想这样做是因为配置中实际上有更多的字典,但我只需要为其中一个字典引发自定义异常,并希望保持数据访问的一致性(全部作为字典)。
Note: This is using Python 2.4.4 注意:这是使用Python 2.4.4
Consider doing this. 考虑这样做。
class MyConfigDict( dict ):
def __getitem__( self, key ):
try:
return super( MyConfigDict, self ).__getitem__( key )
except KeyError as e:
raise MyConfigError( e.message )
Something like that may allow you to wrap every access in your own extended exception. 这样的事情可能允许您在自己的扩展异常中包装每个访问。
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