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Python Error Classes


My primary goal is to follow whatever standard other exception classes have, so that (for instance) any extra string I include in the exception is printed out by whatever tool caught pass The last except clause may omit the exception name(s), to serve as a wildcard. print('y =', y) ... ('spam', 'eggs') ('spam', 'eggs') x = spam y = eggs If an exception has arguments, they are printed as the last part (‘detail') of the Is it good style in modern Python? check over here

It inherits from BaseException instead of Exception so that it is not accidentally caught by code that catches Exception. This is a subclass of IndentationError. Exception handlers don't just handle exceptions if they occur immediately in the try clause, but also if they occur inside functions that are called (even indirectly) in the try clause. exception LookupError¶ The base class for the exceptions that are raised when a key or index used on a mapping or sequence is invalid: IndexError, KeyError. https://docs.python.org/2/library/exceptions.html

Python Custom Exception

exception ImportWarning¶ Base class for warnings about probable mistakes in module imports. return repr(self.value) ... >>> try: ... Avoid passing a dict as a positional argument, future users of your code will thank you.

Look at the following example, which asks the user for input until a valid integer has been entered, but allows the user to interrupt the program (using Control-C or whatever raise KeyboardInterrupt ... In real world applications, the finally clause is useful for releasing external resources (such as files or network connections), regardless of whether the use of the resource was successful. 8.7. Python Filenotfounderror current community chat Stack Overflow Meta Stack Overflow your communities Sign up or log in to customize your list.

self.value = value ... Python Exception Message Many standard modules define their own exceptions to report errors that may occur in functions they define. This behaviour only occurs when constructing OSError directly or via an alias, and is not inherited when subclassing. https://docs.python.org/2.7/tutorial/errors.html SystemErrorRaised when the interpreter finds an internal problem, but when this error is encountered the Python interpreter does not exit.

The TypeError raised by dividing two strings is not handled by the except clause and therefore re-raised after the finally clause has been executed. Python Errno except: ####C ... filename¶ filename2¶ For exceptions that involve a file system path (such as open() or os.unlink()), filename is the file name passed to the function. Raised when a VMS-specific error occurs.

  • print "executing finally clause" ... >>> divide(2, 1) result is 2 executing finally clause >>> divide(2, 0) division by zero!
  • Handlers only handle exceptions that occur in the corresponding try clause, not in other handlers of the same try statement.
  • Is this using Exception.args?
  • exception WindowsError¶ Raised when a Windows-specific error occurs or when the error number does not correspond to an errno value.
  • For example, if the context in which the exception was raised is extra meaningful, then it might be worth storing that context in the Exception: class MyExceptionWithContext(Exception): def __init___(self,dErrorArguments): Exception.__init__(self,"my exception
  • Whatever you put inside an except block will only execute if it catches an exception.
  • TypeError¶ TypeErrors are caused by combining the wrong type of objects, or calling a function with the wrong type of object.
  • exception SyntaxError¶ Raised when the parser encounters a syntax error.

Python Exception Message

It's interesting to know that the arguments passed to the constructor can be retrieved in the args attribute (it's a tuple). –Bastien Léonard Aug 23 '09 at 22:01 1 Hmm, http://stackoverflow.com/questions/1319615/proper-way-to-declare-custom-exceptions-in-modern-python asked 7 years ago viewed 235702 times active 1 month ago Blog Stack Overflow Podcast #92 - The Guerilla Guide to Interviewing Get the weekly newsletter! Python Custom Exception String Services This Page Report a Bug Show Source Quick search Enter search terms or a module, class or function name. Python Raise Valueerror result = x / y ...

exception DeprecationWarning¶ Base class for warnings about deprecated features. check my blog The associated value is a string indicating what went wrong (in low-level terms). Exception¶ Base class for exceptions that do not result in quitting the running application. f1(2) ... Python Exception Class Methods

The default traceback display code shows these chained exceptions in addition to the traceback for the exception itself. python.org/dev/peps/pep-0352 shows what is going on behind the scenes with current Exceptions. If Six Is Easy, Is Ten So Hard? this content except statement has an optional else clause.

print "result is", result ... Python Exception Stack Trace IOErrorRaised when an input/ output operation fails, such as the print statement or the open() function when trying to open a file that does not exist. This can be used to test an exception handler or to report an error condition "just like" the situation in which the interpreter raises the same exception; but beware that there

If you wanted to create MyIndexError, then ask yourself if a regular IndexError would do the trick.

print "caught an exception" ... print('x =', x) ... up vote 595 down vote favorite 158 What's the proper way to declare custom exception classes in modern Python? Python Attributeerror Object Has No Attribute There are at least two possible exceptions: an IOError ValueError Just in case we have an additional unnamed except clause for an unexpected error: import sys try: f = open('integers.txt') s

exception UnicodeError¶ Raised when a Unicode-related encoding or decoding error occurs. Changed in version 2.6: Changed to inherit from BaseException. The associated value is a string indicating the type of the operands and the operation. have a peek at these guys The rest of the line provides detail based on the type of exception and what caused it.

print "no exception" ... Critique of the top answer Maybe I missed the question, but why not: class MyException(Exception): pass Again, the problem with the above is that in order to catch it, you'll either Navigation index modules | next | previous | Python » 2.7.12 Documentation » The Python Standard Library » © Copyright 1990-2016, Python Software Foundation. try: print eval('five times three') except SyntaxError, err: print 'Syntax error %s (%s-%s): %s' % \ (err.filename, err.lineno, err.offset, err.text) print err $ python exceptions_SyntaxError.py Syntax error (1-10): five times

It's possible to "create custom-made" exceptions: With the raise statement it's possible to force a specified exception to occur. except (RuntimeError, TypeError, NameError): ... Syntax Errors 8.2. In any case, you only need the __init__ or __str__ if you do something different from what Exception itself does.

You application will work fine with using message. Please donate. Handling Exceptions 8.4. In real world applications, the finally clause is useful for releasing external resources (such as files or network connections), regardless of whether the use of the resource was successful. 8.7.

Please donate. raise Exception('spam', 'eggs') ... Like so: >>> class OhMyGoodnessExc(Exception): ... Long integers allocate more space as values grow, so they end up raising MemoryError.

Changed in version 2.5: Changed to inherit from BaseException. Word for making your life circumstances seem much worse than they are Jokes about Monica's haircut How do I translate "hate speech"? RuntimeWarning Used for events that happen at runtime that might cause problems. One may also instantiate an exception first before raising it and add any attributes to it as desired. >>> try: ...

But why would you want to do that?