Python fault tolerance,

Python fault tolerance,

# Try: release T: else:

# Why is it fault tolerance? Let's talk about the error first. The error mentioned here is not a bug left in the script because it is so careless or because it cannot be removed. The so-called "let down" means skipping this error, to detect and correct the errors during the test, the fault tolerance error cannot be determined before the script is executed. For example, when a crawler is writing, it crawls to many pages, I don't know whether these pages can be opened or not. It may time out. At this time, the process cannot be stopped due to this error. If there are tens of thousands of addresses, it may take several years to climb. So here we use fault tolerance, skip this error, and write the error into a log. After all the logs are completed, we can check the log to see which pages report errors, then process the batch of pages separately.

# Take opening a file as an Example

# Create 10 files for I in range (10): file_name = 'a_0000d.txt '% I new_file = open (file_name, 'w') new_file.close () # Then read 11 files, note: There are 11 files, that is to say, there must be one file that does not exist, and an error will be reported. Now I want to skip this error and write it into the log # Write the log function and write it one at a time, the name is write_logfor I in range (11): file_name = 'a_0000d.txt '% I # open_file = open (file_name, 'R'). When 11th files are read, an error will be reported when it is 10, so try: open_file = open (file_name, 'R') # There is a possible error code after try t: write_log ('Open file fail! ') # This is the handling of errors. If an error occurs, the open file will be fail! Write logs. This is acceptable, but it is not recommended that you output this error and write it together in the log. The following is the case # The normal syntax is for I in range (11 ): file_name = 'a_0000d.txt '% I try: open_file = open (file_name, 'R') handle T IOError, e: # This IOError is an IO error. If this error occurs, write the error content to the e variable, or change IOError to Exception, so that no matter what error occurs, it will be written to the e variable, but to clarify the error, it is better to specify the Error Type write_log ('% s open file fail! % S') % (file_name, e) # Write the error file name and error message to the log else: open_file.close () # although it is fault tolerant, but the opened files still need to be closed, but they are not opened, that is, 10. They cannot be closed. Therefore, to be added to else, the else function is executed normally, run the command # open_file.close () next to else to write it out. If you want to close it whether it is correct or not, an error will be reported when you open it 10, that is, it is not opened at all. Why should we close it?

I forgot to add a bunch of errors and copied them. There are many Baidu websites. For details, refer

Exception name	Description
BaseException	All abnormal base classes
SystemExit	Interpreter request to exit
KeyboardInterrupt	User interrupted execution (usually input ^ C)
Exception	Base class with regular errors
StopIteration	The iterator does not have more values.
GeneratorExit	Generator exception to notify exit
StandardError	All base classes with built-in standard exceptions
ArithmeticError	Base classes with incorrect numeric calculation
FloatingPointError	Floating Point Calculation Error
OverflowError	The value operation exceeds the maximum limit.
ZeroDivisionError	Except (or modulo) zero (all data types)
AssertionError	Assertion statement failed
AttributeError	The object does not have this property.
EOFError	No built-in input, reaching the EOF tag
EnvironmentError	Operating System Error base class
IOError	Input/Output operation failed
OSError	Operating System Error
WindowsError	System Call failed
ImportError	Import module/object failed
LookupError	Base class for invalid data query
IndexError	This index is not found in the sequence)
KeyError	The ing does not contain this key.
MemoryError	Memory overflow error (not fatal for Python Interpreter)
NameError	Object not declared/initialized (no attribute)
UnboundLocalError	Access uninitialized local variables
ReferenceError	Weak reference attempts to access garbage collection objects
RuntimeError	General running errors
NotImplementedError	Unimplemented Methods
SyntaxError	Python syntax error
IndentationError	Indentation Error
TabError	Mix Tab and Space
SystemError	General interpreter system error
TypeError	Operation that is invalid for the Type
ValueError	Invalid parameter passed in
UnicodeError	Unicode errors
UnicodeDecodeError	Unicode decoding error
UnicodeEncodeError	Unicode Encoding Error
UnicodeTranslateError	Unicode Conversion error
Warning	Warning base class
DeprecationWarning	Warning about discarded features
FutureWarning	Warning about future semantic changes in Construction
OverflowWarning	Old warning about automatic upgrade to long (long)
PendingDeprecationWarning	Warning that features will be discarded
RuntimeWarning	Warning of suspicious running behavior (runtime behavior)
SyntaxWarning	Warning of suspicious syntax
UserWarning	Warning generated by user code