python-Exception Handling

First, catch the exception

1, when the program error, will not show the bug information to the user, but to provide a friendly prompt, continue to execute the program

2, the following, to achieve division, when the denominator is 0 o'clock, capture and print out the exception information; exception can catch any exception

def Div (x, y):     Try :         Print (x/y)     except Exception as E:         Print (' exception is ', E)

>>> Div (1,0)
Exception is division by zero

You can also specify that the exception is Zerodivisionerror

def Div (x, y):     Try :         Print (x/y)     except Zerodivisionerror as E:         Print (' exception is ', E)

>>> Div (1,0)
Exception is division by zero

3. Capturing multiple exceptions at the same time

deffdiv (x, y):Try:        returnx/yexceptTypeError as E:Print('TypeError:', E)exceptZerodivisionerror as E:Print('Zerodivisionerror:', E)exceptException as E:Print('Other Exceptions:'E

>>> fdiv (' ABC ', 0)
typeerror:unsupported operand type (s) for/: ' str ' and ' int '
>>> Fdiv (12,0)
Zerodivisionerror:division by Zero

You can also use the following methods:

def fdiv1 (x, y    ): Try :         return x/y    except  (TypeError, Zerodivisionerror, Exception) as E:         Print (e)


>>> fdiv1 (' ABC ', 0)
Unsupported operand type (s) for/: ' str ' and ' int '
>>> Fdiv1 (12,0)
Division by zero

Second, common anomalies

'---------------IOError: Open File path error or not present------------------'Try: F= Open ('Error.txt','R')exceptIOError as E:Print('Error opening file:', E)'--------------importerror: The Import module path is faulty or does not exist--------------'Try:    ImportErrorexceptImporterror as E:Print('Import module error, error message:', E)'--------------indexerror: Index out of bounds----------------------------'List1= [1,2,3,4,5,6]Try:    Print(list1[6])exceptIndexerror as E:Print('Query list error, error message:', E)'----------------keyerror: Find a keyword that does not exist in the dictionary---------------'Dict1= {1:'A', 2:'B'}Try:    Print(dict1[3])exceptKeyerror as E:Print('Query dictionary error, error message:', E)'----------------TypeError: Parameter types do not match----------------------'defFint (a):Print(A/2)Try: str1='ABC'Fint (str1)exceptTypeError as E:Print('parameter type error, error message:', E)'------------valueerror: The parameter type matches, but the value passed in is not------------'str1='ABC'Try:    Print(int (str1))exceptValueError as E:Print('parameter value error, error message:', E)'------------------nameerror: The variable used is not assigned a value------------------'Try:    Print(a)exceptNameerror as E:Print('parameter error, error message:'E

Third, custom exceptions

class myexception (Exception):     def __init__ (Self, msg):         = msg    def__str__(self):        return  self.message  try:    raise myexception (' Custom exception ' ) )except  myexception as E:    print(e)

Four, the initiative throws the exception

Try :     Raise IOError (' Error reading/writing file ')  # actively throws IOError exception except  IOError as E:    print(e)

Wu, try-except-else-finally

Try: F= Open ('Test.txt','R')exceptIOError as E:#打开文件失败, youThrow Exception    Print(e)Else:#The open file succeeds, then the else block is executed    Print('Execute Else') F.close ()finally:#the finally block executes regardless of whether the file is open properly    Print('Execute finally')

python-Exception Handling