此代碼演示例外的功能是什麼？

我正在從「絕對初學者的Python」一書中學習，並且學習了關於異常的章節。作者的解釋越來越短，並且對於這段代碼，我完全困惑，並且沒有任何解釋！有人可以一行一行解釋嗎？此代碼演示例外的功能是什麼？

#!/usr/bin/env python 
store = [] 
try: {}["foo"] 
except KeyError as e: store.append(e) 
try: 1/0 
except ZeroDivisionError as e: store.append(e) 
try: "".bar() 
except AttributeError as e: store.append(e) 
for exceptionobject in store: 
    ec = exceptionobject.__class__ 
    print(ec.__name__) 
    indent = " +-" 
    while ec.__bases__: 
     ec = ec.__bases__[0] 
     print(indent + ec.__name__) 
     indent = " " + indent

來源

2012-03-08 Billjk

# create a list 
store = [] 

try: 
    # if something in this block would throw an exception, 
    # code could continue in a controlled way in an except block 

    # force a KeyError by looking up a non-existent key in an empty dictionary 
    {}["foo"] 

except KeyError as e: 
    # store the exception object in the list 
    store.append(e) 

# same scheme here; construct something that fails (1/0), 
# then instead of quitting the interpreter, continue operations 
try: 
    1/0 
except ZeroDivisionError as e: 
    store.append(e) 

# pythons exceptions hierarchy is diverse and exceptions carry meaningful 
# names expressing their context 
try: 
    # here we attept to lookup an attribute (that's happening technically 
    # before the call), which does not exists (because strings don't know 
    # how to bar... 
    "".bar() 

except AttributeError as e: 
    # ... and the the appropriate exception here is AttributeError 
    store.append(e)

此時列表中有三個元素，它們是異常對象。

# loop over list 
for exceptionobject in store: 

    # get the class of the object via special method __class__ 
    # __class__ returns an object whose class is type actually; 
    # but don't be too confused by this 
    ec = exceptionobject.__class__ 

    # print the name of the exception class, now this is just a plain string 
    print(ec.__name__) 

    indent = " +-" 

    # use another special method __bases__ to get all superclasses 
    # of the exception class; all exceptions inherit from BaseException 
    # loop over the base classes 
    while ec.__bases__: 

     # get the first base class 
     ec = ec.__bases__[0] 

     # print its name an indent more 
     print(indent + ec.__name__) 
     indent = " " + indent

結果應該是這個樣子：

KeyError 
+-LookupError 
    +-StandardError 
    +-Exception 
    +-BaseException 
    +-object 
ZeroDivisionError 
+-ArithmeticError 
    +-StandardError 
    +-Exception 
    +-BaseException 
    +-object 
AttributeError 
+-StandardError 
    +-Exception 
    +-BaseException 
    +-object

顯示exception hierarchy的一部分。

來源

2012-03-08 02:06:04 miku

上半年（具有三個except條款），它只是在關鍵字後力是很醒目（你趕上與except關鍵字例外）非常相同的異常，然後在異常處理程序（代碼;它在異常發生時運行，或者產生了）它將每個異常都添加到列表中。

在下半部分，它會遍歷保存的異常（現在列表中的異常）並顯示它們的一些屬性。

從這個練習中，你或許應該拿走主要是你如何捕捉異常，其次纔是一個事實，即一個例外是一個對象，就像一切都在Python：

In [6]: KeyError.__class__ 
Out[6]: type

「類型」是類的類在Python中 - 這幾乎是一種語言的怪癖，如果你沒有得到這個，你不應該很快擔心它。無論如何，這一點表明一個例外是一個類。

In [7]: err = KeyError() 
In [8]: err.__class__ 
Out[8]: KeyError

在這裏，我們實例化一個KeyError異常的對象，這是一件好事，當一個KeyError異常異常發生時，可自動發生（err在這種情況下是一樣的，在異常處理e在你的代碼）。正如你所看到的那樣，err的等級是KeyError。

來源

2012-03-08 01:49:02

此代碼演示例外的功能是什麼？

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