Exceptions for Python

I. Common forms of anomalies

An exception is an event that occurs during program execution and affects the normal execution of the program. In general, an exception occurs when Python does not handle the program properly. The exception is a Python object that represents an error. When a Python script exception occurs, we need to capture and process it, or the program terminates execution.

You can use the Try/except statement to catch an exception. The try/except statement is used to detect errors in a try statement block, allowing the except statement to catch exception information and handle it. If you do not want to end your program when an exception occurs, simply capture it in a try. The following is a simple syntax for try....except...else:

Try :< statements >        # Run other code except < name >:< statement >        # if the ' name ' exception is thrown in the try section except < name >,< data >:< statement >        # if the ' name ' exception is thrown, get additional data Else :< statement >        # If no exception occurs
Finally
< statements >

Try works by starting a try statement, and Python is tagged in the context of the current program so that when an exception occurs, it can go back here, the TRY clause executes first, and what happens next depends on whether an exception occurs at execution time.

• If an exception occurs when the statement after the try is executed, Python jumps back to the try and executes the first except clause that matches the exception, and the control flow passes through the entire try statement (unless a new exception is thrown when the exception is handled).
• If an exception occurs in the statement after the try, but there is no matching except clause, the exception will be submitted to the upper try, or to the top of the program (This will end the program and print the default error message).
• If no exception occurs when the TRY clause executes, Python executes the statement after the Else statement (if there is else), and then the control flow passes through the entire try statement.
• Finally statement: Whether or not catch exception finally is the last need to execute.

Examples are as follows:

Try: A= 10b=0 A/bexceptException as E:Print(e)Print('Error')Else:    Print('This is ok!')finally:    Print('End') A= [1,2,4]Try:    Print(a[4])exceptIndexerror as E:Print(e)

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Second, exception handling methods

Excepthion is all of the exception base classes (), for Python standard exceptions, we listed below for reference:

Exception name	Describe
Baseexception	base class for all exceptions
Systemexit	Interpreter Request exited
Keyboardinterrupt	User interrupt execution (usually input ^c)
Exception	base class for general errors
Stopiteration	There are no more values for iterators
Generatorexit	Generator (generator) exception occurred to notify exit
StandardError	Base class for all built-in standard exceptions
Arithmeticerror	base class for all numeric calculation errors
Floatingpointerror	Floating-point calculation error
Overflowerror	Numeric operation exceeds maximum limit
Zerodivisionerror	Except (or modulo) 0 (all data types)
Assertionerror	Assertion statement failed
Attributeerror	Object does not have this property
Eoferror	No built-in input, EOF Mark reached
EnvironmentError	Base class for operating system errors
IOError	Input/output operation failed
OSError	Operating system error
Windowserror	System call failed
Importerror	Failed to import module/object
Lookuperror	base class for invalid data queries
Indexerror	This index is not in the sequence (index)
Keyerror	This key is not in the map
Memoryerror	Memory overflow error (not fatal for Python interpreter)
Nameerror	Object not declared/initialized (no attributes)
Unboundlocalerror	To access uninitialized local variables
Referenceerror	Weak references (Weak reference) attempt to access objects that have been garbage collected
RuntimeError	General run-time errors
Notimplementederror	Methods that have not been implemented
SyntaxError	Python syntax error
Indentationerror	Indentation Error
Taberror	Tab and Space Mix
Systemerror	General Interpreter system error
TypeError	An operation that is not valid for type
ValueError	Invalid parameter passed in
Unicodeerror	Unicode-related errors
Unicodedecodeerror	Error in Unicode decoding
Unicodeencodeerror	Unicode encoding Error
Unicodetranslateerror	Unicode Conversion Error
Warning	Base class for warnings
Deprecationwarning	Warnings about deprecated features
Futurewarning	Warning about the change in the construction of future semantics
Overflowwarning	Old warning about auto-promotion to Long integer
Pendingdeprecationwarning	Warnings about attributes that will be discarded
Runtimewarning	Warning for suspicious run-time behavior (runtime behavior)
Syntaxwarning	Warning of suspicious syntax
Userwarning	Warnings generated by user code

Third, the use of raise keywords

The raise statement is used to trigger an exception with the following syntax:

Raise [Exception [, Args [, Traceback]]

The type of exception in the statement is an exception (for example, the Nameerror) parameter is an exception parameter value. This parameter is optional and if not provided, the exception parameter is "None". The last parameter is optional (rarely used in practice) and, if present, is the tracking exception object.

Examples of procedures are as follows:

Try: A= 10b=0 A/bexceptException as E:Print(e)Print('Error')    RaiseeElse:    Print('This is ok!')finally:    Print('End')Print('Hello')

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Exceptions for Python