Python Fault tolerance

#try: Except:else:

#为什么叫容错呢, first of all to say that the mistake here is not because of sloppy or any reason in the script left the bug, this can not be allowed, the so-called tolerance is to skip this error, to be found and fixed in the test, the need to fault-tolerant error is not before the script execution can not determine whether the error is wrong, For example: In the writing crawler, will crawl to many pages, these pages I do not know can open, it is possible to timeout, this time can not be because of this error to stop the process to find the problem, then if there are tens of thousands of addresses, estimated to use a few years to climb. So here is the use of fault-tolerant, jump over this error, and write the error to a log, and so on, then to check the log, see which pages report errors, and then separate this batch of pages to process

#以打开文件为例

#Create 10 files first forIinchRange (10): file_name='A_%d.txt'%I new_file= Open (file_name,'W') New_file.close ()#then read 11 files, note, is 11 files, that is, there is a file must not exist, then will be an error, now I want to skip this mistake, and write to the log#Write log function One will write one, the name is called Write_log forIinchRange (11): file_name='A_%d.txt'%I#open_file = open (file_name, ' R ') when the 11th file is read, it will be error 10, so it cannot be  Try: Open_file= Open (file_name,'R')#the code behind the try is a possible error  except: Write_log ('Open File fail!')#this is wrong to deal with, that is, the open file fail! will be written to the log, this is possible, but not recommended, it is best to put this error output, and write together in the log, is the following#normal wording forIinchRange (11): file_name='A_%d.txt'%ITry: Open_file= Open (file_name,'R')  exceptIOError, E:#This ioerror is an IO error, that is, if it is the wrong words, the error is written in the e variable, you can also change the ioerror to exception, so whatever error, will be written to the e variable, but in order to clarify the error, or to specify the wrong type is better Write_log ('%s Open File fail!%s')% (file_name,e)#write the wrong file name and error content to the log  Else: Open_file.close ()#Although it is fault-tolerant, but the open file is still to be closed, but not open, that is, 10, cannot be closed, so to add to the else, else the function is normal execution, and then execute the command after the Else  #Open_file.close () This is to write off the outside, think whether the right or not to close, then open 10 when the error, that is, no open, then how to close it

Forgot to add a bunch of error, this is copied, Baidu has a lot, you can refer to the next

Exception name	Description
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

Python Fault tolerance