Relever manuellement une exception dans Python

91

raise ValueError('A very specific bad thing happened.') 

raise Exception('I know Python!') # Don't! If you catch, likely to hide bugs. 

def demo_bad_catch():     try:         raise ValueError('Represents a hidden bug, do not catch this')         raise Exception('This is the exception you expect to handle')     except Exception as error:         print('Caught this error: ' + repr(error))  >>> demo_bad_catch() Caught this error: ValueError('Represents a hidden bug, do not catch this',) 

def demo_no_catch():     try:         raise Exception('general exceptions not caught by specific handling')     except ValueError as e:         print('we will not catch exception: Exception')    >>> demo_no_catch() Traceback (most recent call last):   File "<stdin>", line 1, in <module>   File "<stdin>", line 3, in demo_no_catch Exception: general exceptions not caught by specific handling 

raise ValueError('A very specific bad thing happened') 

raise ValueError('A very specific bad thing happened', 'foo', 'bar', 'baz')  

try:     some_code_that_may_raise_our_value_error() except ValueError as err:     print(err.args) 

('message', 'foo', 'bar', 'baz')     

logger = logging.getLogger(__name__)  try:     do_something_in_app_that_breaks_easily() except AppError as error:     logger.error(error)     raise                 # just this!     # raise AppError      # Don't do this, you'll lose the stack trace! 

type, value, traceback = sys.exc_info() 

raise AppError, error, sys.exc_info()[2] # avoid this. # Equivalently, as error *is* the second object: raise sys.exc_info()[0], sys.exc_info()[1], sys.exc_info()[2] 

def error():     raise ValueError('oops!')  def catch_error_modify_message():     try:         error()     except ValueError:         error_type, error_instance, traceback = sys.exc_info()         error_instance.args = (error_instance.args[0] + ' <modification>',)         raise error_type, error_instance, traceback 

>>> catch_error_modify_message() Traceback (most recent call last):   File "<stdin>", line 1, in <module>   File "<stdin>", line 3, in catch_error_modify_message   File "<stdin>", line 2, in error ValueError: oops! <modification> 

raise error.with_traceback(sys.exc_info()[2]) 

raise RuntimeError('specific message') from error 

raise ValueError, 'message' # Don't do this, it's deprecated! 

raise 'message' # really really wrong. don't do this. 

def api_func(foo):     '''foo should be either 'baz' or 'bar'. returns something very useful.'''     if foo not in _ALLOWED_ARGS:         raise ValueError('{foo} wrong, use "baz" or "bar"'.format(foo=repr(foo))) 

class MyAppLookupError(LookupError):     '''raise this when there's a lookup error for my app''' 

if important_key not in resource_dict and not ok_to_be_missing:     raise MyAppLookupError('resource is missing, and that is not ok.') 

80

raise Exception("I know python!") 

73

1. raise exception  2. raise exception (args)  3. raise 4. raise exception (args) from original_exception 

  #raise exception (args)     try:         raise ValueError("I have raised an Exception")     except ValueError as exp:         print ("Error", exp)     # Output -> Error I have raised an Exception       #raise execption      try:         raise ValueError     except ValueError as exp:         print ("Error", exp)     # Output -> Error  

def somefunction():     print("some cleaning")  a=10 b=0  result=None  try:     result=a/b     print(result)  except Exception:            #Output ->     somefunction()           #some cleaning     raise                    #Traceback (most recent call last):                              #File "python", line 8, in <module>                              #ZeroDivisionError: division by zero 

class MyCustomException(Exception): pass  a=10 b=0  reuslt=None try:     try:         result=a/b      except ZeroDivisionError as exp:         print("ZeroDivisionError -- ",exp)         raise MyCustomException("Zero Division ") from exp  except MyCustomException as exp:         print("MyException",exp)         print(exp.__cause__) 

ZeroDivisionError --  division by zero MyException Zero Division  division by zero 

64

if 0 < distance <= RADIUS:     #Do something. elif RADIUS < distance:     #Do something. else:     raise AssertionError("Unexpected value of 'distance'!", distance) 

50

raise SystemExit 

raise SystemExit("program exited")