Python (Exception Processing)

Exception Handling

1. The exception handling action is:

• I do not want to terminate the program
• If something goes wrong, it requires special handling to ensure the stability and robustness of the program

2. Capture exception can use try / except statement

• try / except statement is used to detect errors in the try block, so that the abnormality information except statement capture and processing.
• If you do not want to end your program when an exception occurs, simply try to capture it in.

 3. Syntax 1

• try ... except ... else ...
• When no exception occurs, else statements will be executed
• When there is an abnormality in the try block error, except in the code block is executed
• You can not pass the processing result placeholders

# Catch all exceptions a 
the try :
    ...
except:
    ...
else:
    ...

# Catch all exceptions two 
the try :
    ...
except Exception,e:
    print e
else:
    ...

# Simultaneously capture multiple exceptions, simultaneous processing, the same reaction to make the different exception 
the try :
    Listing 1
the except (error type 1, type 2 error, the error type 3, ...):
    Code segment 2
else:
    ...

# Simultaneously capture multiple exceptions, simultaneous processing, react differently to different exception 
the try :
    Listing 1
the except (Error Type 1):
    Code segment 2
the except (error type 2):
    Code segment 3
except（...）：
    ...
else:
    ...

 Example:

# Specifies the exception type 
the try :
    FH = Open ( " d: \\ testfile " , " r " )
     Print fh.read ()
 the except IOError:
     Print  " Error: file not found or read the file failed ," 
the else :
     Print  " content written to the file successfully ."
    fh.close()

# Get abnormality by Exception 
the try :
     . 1/ 0
 the except Exception, E:
     Print E
 the else :
     Print  " OK "

# Used except without any exception type with 
the try :
     . 1/ 0
 except :
     Print  " error " 
the else :
     Print  " OK "

 4. Syntax 2

• try ... except ... finally ...
• Whether or not an exception will be executed finally captured

try：
    Listing 1
the except (error type 1, type 2 error, the error type 3, ......):
    Code segment 2
finally：
    Code segment 3

The initiative thrown

grammar:

• raise the types of errors - to raise the program execution when an exception is thrown directly
• Note: Error type must be a class, and this class is a subclass of Exception

# Input the age, if the input age range 0-100 not, the program would crash 
Age = int (INPUT ( ' Age: ' ))
 IF Age> 100 or Age < 0:
     The raise a ValueError

 6.python standard abnormality as follows

BaseException	Base class for all exceptions
SystemExit	Interpreter exit request
KeyboardInterrupt	User Interrupt Executing (usually enter ^ C)
Exception	General Error base class
StopIteration	Iterator no more value
GeneratorExit	To notify the exit exception generator (generator) occurs
StandardError	All standard exceptions built base class
ArithmeticError	All numerical errors base class
FloatingPointError	Floating-point calculation error
OverflowError	Exceeds the maximum limit value calculation
ZeroDivisionError	In addition to (or modulus) of zero (all data types)
AssertionError	Assertion failure
AttributeError	Object does not have this property
EOFError	No built-in input, to reach the EOF marker
EnvironmentError	OS Error base class
IOError	Input / output operations to fail
OSError	Operating system error
WindowsError	System call fails
ImportError	Import module / object failed
LookupError	Invalid class data base query
IndexError	Without this sequence index (index)
KeyError	Without this key mapping
MemoryError	Memory overflow error (for Python interpreter is not fatal)
NameError	Undeclared / initialize objects (no attributes)
UnboundLocalError	Local access uninitialized variables
ReferenceError	Weak reference object (Weak reference) have been trying to access a garbage collection of
RuntimeError	General runtime error
NotImplementedError	The method has not been implemented
SyntaxError	Python syntax error
IndentationError	Indentation errors
TabError	Tab and space mix
SystemError	General interpreter system error
TypeError	Invalid type of operation
ValueError	Invalid parameter passed
UnicodeError	Unicode related errors
UnicodeDecodeError	Error when decoding of Unicode
UnicodeEncodeError	Unicode encoding error
UnicodeTranslateError	Unicode conversion error
Warning	Warning base class
DeprecationWarning	Warning about deprecated features
FutureWarning	Warning about the future structure of the semantics have changed
overflow Warning	The old warning about automatically promoted to a long integer (long) of
PendingDeprecationWarning	Will be warned about the characteristics of the waste
RuntimeWarning	Suspicious behavior (runtime behavior) run-time warning
SyntaxWarning	Suspicious Warning grammar
UserWarning	User code generated warning