This article shares with you the main isPythoncommon mistakes and exceptions and how to deal with them, let's take a look at it and hope toLearningPython has helped. 1. How errors and exceptions are handled 1. Common Mistakes 1. A:Nameerror 2. If True:SyntaxError 3. F = OEPN (' 1.txt '):IOError 4.10/0:Zerodivisionerror 5. A = Int (' d '):ValueError 6.program run Interrupt:Keyboardinterrupt 2.python- Handling Exceptions using try_except (1) Try: Try_suiteexceptException [E]: Exception_block 1. Tryused to captureTry_suitethe error in,and give the error toexceptprocessing 2. Exceptused to handle exceptions,If handling exceptions and setting catch exceptions are consistent,UseException_blockHandling Exceptions # case 1Try: Undefexcept: Print' Catch an except ' # case 2Try: ifUndefexcept: Print' Catch an except ' · Case1: Can catch exception because it is a run-time error · Case2: Cannot catch exception because it is a syntax error, pre-run error -- # Case 3Try: UndefexceptNameerror,e: Print' Catch an except ', E # Case 4Try: UndefexceptIoerror,e: Print' Catch an except ', E · Case3: You can catch exceptions because the settings captureNameerrorException · Case4: Cannot catch exception because the settingIOError, will not processNameerror Example ImportRandom num = random.randint (0, 100) whileTrue: Try: guess = Int (raw_input ("Enter 1~100")) Except ValueError, E: Print "Enter 1~100" Continue ifGuess > num: Print "Guess bigger:", guess Elif Guess < num: Print "Guess Smaller:", guess Elif guess = = num: Print "Guess ok,game over" Break print ' \ n ' 3. Python handles exceptions using try_except (2) · Try-except: Handling Multiple exceptions Try: Try_suiteexceptException1[e]: Exception_block1exceptException2[e]: Exception_block2exceptExceptionn[e]: Exception_blockn 4. python-try_finally use Try: Try_suitefinally: Do_finally ·ifTrystatement does not catch error, code executiondo_finallyStatement ·ifTryThe statement captures the error and the program first executesdo_finallystatement, and then give the captured error to thepythonInterpreter Processing 5. Python-try-except-else-finally Try: Try_suite except: Do_except finally: Do_finally ·ifTryThe statement does not catch an exception and executesTrycode snippet, executefinally ·ifTrycatch exception, first executeexcepthandle the error, and then executefinally 6. Python-with_as Statements withContext[ASvar]: With_suite · Withstatement to replaceTry_except_finallstatement to make the code more concise · Contextexpression Return is an object · Varused to saveContextreturns an object, a single return value, or a meta-ancestor · With_suiteUsevarvariable toContextreturning an object for action The With statement is essentially context management : 1.Context Management Protocol: Containment Method__enter__ ()and the__exit()__ ,The object that supports this protocol is to implement both methods 2.Context Manager: Define execution withstatement is the runtime context to be established, which is responsible for executing the withentry and exit operations in the context of a statement block 3.into the context Manager: Call Manager__enter__method, if you set theas Varstatement,varVariable Acceptance__enter__ ()method return value 4.Exit Context Manager: Call Manager__exit__Method classMycontex(object): def__init__(self, name): Self.name = Name def__enter__(self): Print"__enter__" returnSelf defdo_self(self): Print"Do_self" def__exit__(Self, Exc_type, Exc_val, EXC_TB): Print"__exit__" Print"Error:", Exc_type, "info:", exc_val if__name__ = = "__main__": withMycontex (' Test context ') asF: PrintF.name F.do_self () whith Statement Application scenario: 1.file Operations 2.mutually exclusive objects, such as mutexes, between process threads 3.other objects that support context 2. standard exception and automatic with exception 1. Python-assert and raise statements · RaisStatement · Reisestatements are used to actively throw exceptions ·syntax Format:Raise[exception[,args]] · exception: Exception class · Args: A tuple that describes the exception information RaiseTypeError, ' Test Error ' RaiseIOError, ' File not Exit ' · AssertStatement ·Assertion Statement:assertstatement is used to detect whether an expression is true, if false, to throwAssertionerrorError ·syntax Format:assert Expression[,args] · Experession: An expression · Args: The descriptive information of the judging condition Assert 0, ' test assert ' Assert 4==5, ' Test assert ' 2. python- Standard exceptions and custom exceptions ·Standard Exceptions · Pythonbuilt-in exceptions that existed before the program was executed · ·Custom Exceptions: · Pythonallow custom exceptions to describepythonNo exceptions are involved in the ·custom exceptions must inheritExceptionclass ·custom exceptions can only be triggered proactively classCustomerror(Exception): def__init__(self, info): Exception.__init__ (self) Self.message = info PrintID (self) def__str__(self): return' custionerror:%s '% self.message Try: RaiseCustomerror (' Test customerror ')exceptCustomerror, E: Print' errorinfo:%d,%s '% (ID (e), E) Source:Blog Park
Python Error and exception concepts
