錯誤Error:

• 邏輯錯誤: 演算法錯誤, - => +
• 筆誤: 變數名錯誤,語法錯誤
• 函式或類使用錯誤
• 錯誤可以避免

異常Exception:

• 本身就是意外情況
• 前提時沒有出現上面的錯誤,即程式寫的沒有問題,但是某些情況下,會出現一些意外,導致程式無法正常執行下去
• open函式操作一個檔案,檔案不存在,或者建立一個檔案時,檔案已經存在了,或者訪問一個網路檔案,斷網了,這都是異常,是意外情況
• 異常不可能避免

錯誤和異常:

在高階程式語言中,一般都有錯誤和異常的概念,異常可以捕獲,並加以處理,但是錯誤是不能被捕獲的

異常: 編譯器對異常具有跟蹤機制

錯誤:

產生異常:

• raise 語句顯式丟擲異常
• Python直譯器自己檢測到異常並引發

def ore():
    print('before')
    def lap():
        print(1/0)
    lap()
    print('after')
ore()

def ore():
    print('before')
    raise Exception('exception!')
    print('after')
ore()

程式會在異常丟擲的地方中斷執行,如果不捕獲異常,就會提前結束程式

raise語句:

raise後什麼都沒有,表示丟擲最近一個被啟用的異常,如果沒有被啟用的異常,則拋RuntimeError異常

raise後要求應該是BaseException類或其子類或它們的例項,如果是類,將被無參例項化

try:
    1/0
except BaseException:
    try:
        raise
    except Exception as f:
        print(f)

BaseException
+-- SystemExit
+-- KeyboardInterrupt
+-- GeneratorExit
+-- Exception
+-- StopIteration
+-- StandardError
| +-- BufferError
| +-- ArithmeticError
 
| | +-- FloatingPointError
| | +-- OverflowError
| | +-- ZeroDivisionError
| +-- AssertionError
| +-- AttributeError
| +-- EnvironmentError
| | +-- IOError
| | +-- OSError
| | +-- WindowsError (Windows)
| | +-- VMSError (VMS)
| +-- EOFError
| +-- ImportError
| +-- LookupError
| | +-- IndexError
| | +-- KeyError
| +-- MemoryError
| +-- NameError
| | +-- UnboundLocalError
| +-- ReferenceError
| +-- RuntimeError
| | +-- NotImplementedError
| +-- SyntaxError
| | +-- IndentationError
| | +-- TabError
| +-- SystemError
| +-- TypeError
| +-- ValueError
| +-- UnicodeError
| +-- UnicodeDecodeError
| +-- UnicodeEncodeError
| +-- UnicodeTranslateError
+-- Warning
+-- DeprecationWarning
+-- PendingDeprecationWarning
+-- RuntimeWarning
+-- SyntaxWarning
+-- UserWarning
+-- FutureWarning
+-- ImportWarning
+-- UnicodeWarning
+-- BytesWarning
+– ResourceWarning

異常的捕獲:

try:
    code block
except [except type]:
    dealing except

try:
    print('aaaaaaaaaaa')
    print(1/0)
    print('bbbbbbbbbbb')
except:
    print('catch exception')
print('outer')

捕獲指定型別的異常

try:
    print('aaaaaaaaaaa')
    print(1/0)
    print('bbbbbbbbbbb')
except ArithmeticError:
    print('catch exception')
print('outer')

異常類及繼承層次

BaseException
+-- SystemExit
+-- KeyboardInterrupt
+-- GeneratorExit
+-- Exception
+-- StopIteration
+-- StandardError
| +-- BufferError
| +-- ArithmeticError
| | +-- FloatingPointError
| | +-- OverflowError
| | +-- ZeroDivisionError
| +-- AssertionError
| +-- AttributeError
| +-- EnvironmentError
| | +-- IOError
| | +-- OSError
| | +-- WindowsError (Windows)
| | +-- VMSError (VMS)
| +-- EOFError
| +-- ImportError
| +-- LookupError
| | +-- IndexError
| | +-- KeyError
| +-- MemoryError
| +-- NameError
| | +-- UnboundLocalError
| +-- ReferenceError
| +-- RuntimeError
| | +-- NotImplementedError
| +-- SyntaxError
| | +-- IndentationError
| | +-- TabError
| +-- SystemError
| +-- TypeError
| +-- ValueError
| +-- UnicodeError
| +-- UnicodeDecodeError
| +-- UnicodeEncodeError
| +-- UnicodeTranslateError
+-- Warning
+-- DeprecationWarning
+-- PendingDeprecationWarning
+-- RuntimeWarning
+-- SyntaxWarning
+-- UserWarning
+-- FutureWarning
+-- ImportWarning
+-- UnicodeWarning
+-- BytesWarning
+– ResourceWarning

python所有的標準異常類：

python所有的標準異常類：