Python Error Types Ioerror
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a try statement with an except clause that mentions a particular class, that clause also handles any exception classes derived from that class (but not exception classes type error python from which it is derived). Two exception classes that are not related via python valueerror example subclassing are never equivalent, even if they have the same name. The built-in exceptions listed below can be generated by python filenotfounderror the interpreter or built-in functions. Except where mentioned, they have an "associated value" indicating the detailed cause of the error. This may be a string or a tuple of several items of information python custom exception (e.g., an error code and a string explaining the code). The associated value is usually passed as arguments to the exception class's constructor. User code can raise built-in exceptions. 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 is nothing to prevent user code from
Python Exception Message
raising an inappropriate error. The built-in exception classes can be subclassed to define new exceptions; programmers are encouraged to derive new exceptions from the Exception class or one of its subclasses, and not from BaseException. More information on defining exceptions is available in the Python Tutorial under User-defined Exceptions. When raising (or re-raising) an exception in an except or finally clause __context__ is automatically set to the last exception caught; if the new exception is not handled the traceback that is eventually displayed will include the originating exception(s) and the final exception. When raising a new exception (rather than using a bare raise to re-raise the exception currently being handled), the implicit exception context can be supplemented with an explicit cause by using from with raise: raise new_exc from original_exc The expression following from must be an exception or None. It will be set as __cause__ on the raised exception. Setting __cause__ also implicitly sets the __suppress_context__ attribute to True, so that using raise new_exc from None effectively replaces the old exception with the new one for display
you have probably seen some. There are (at least) two distinguishable kinds of errors: syntax errors and exceptions. 8.1. Syntax Errors¶ Syntax errors, also known as parsing errors, are
Python Exception Class Methods
perhaps the most common kind of complaint you get while you are still python errno learning Python: >>> while True print 'Hello world' File "
Exception StandardError ArithmeticError LookupError EnvironmentError Raised Exceptions AssertionError AttributeError EOFError FloatingPointError GeneratorExit IOError ImportError IndexError KeyError KeyboardInterrupt MemoryError NameError NotImplementedError OSError OverflowError ReferenceError RuntimeError StopIteration SyntaxError SystemError SystemExit https://pymotw.com/2/exceptions/ TypeError UnboundLocalError UnicodeError ValueError ZeroDivisionError Warning Categories Navigation Table of Contents Previous: Built-in Objects http://stackoverflow.com/questions/12283377/are-python-error-numbers-associated-with-ioerror-stable Next: String Services This Page Show Source Examples The output from all the example programs from PyMOTW has been generated with Python 2.7.8, unless otherwise noted. Some of the features described here may not be available in earlier versions of Python. If you are looking for examples that work under Python 3, please python exception refer to the PyMOTW-3 section of the site. Navigation index modules | next | previous | PyMOTW » Built-in Objects » exceptions - Built-in error classes¶ Purpose:The exceptions module defines the built-in errors used throughout the standard library and by the interpreter. Available In:1.5 and later Description¶ In the past, Python has supported simple string messages as exceptions as well as classes. Since 1.5, all of python error types the standard library modules use classes for exceptions. Starting with Python 2.5, string exceptions result in a DeprecationWarning, and support for string exceptions will be removed in the future. Base Classes¶ The exception classes are defined in a hierarchy, described in the standard library documentation. In addition to the obvious organizational benefits, exception inheritance is useful because related exceptions can be caught by catching their base class. In most cases, these base classes are not intended to be raised directly. BaseException¶ Base class for all exceptions. Implements logic for creating a string representation of the exception using str() from the arguments passed to the constructor. Exception¶ Base class for exceptions that do not result in quitting the running application. All user-defined exceptions should use Exception as a base class. StandardError¶ Base class for built-in exceptions used in the standard library. ArithmeticError¶ Base class for math-related errors. LookupError¶ Base class for errors raised when something can't be found. EnvironmentError¶ Base class for errors that come from outside of Python (the operating system, filesystem, etc.). Raised Exceptions¶ AssertionError¶ An AssertionError is raised by a failed assert statement. assert False, 'The assertion failed' $ python exceptions_AssertionError_assert.py Traceback (most recent call la
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 6.2 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up Are Python error numbers associated with IOError stable? up vote 4 down vote favorite I want to move a file, but in the case it is not found I should just ignore it. In all other cases the exception should be propagated. I have the following piece of Python code: try: shutil.move(old_path, new_path) except IOError as e: if e.errno != 2: raise e errno == 2 is the one, that has 'No such file or directory' description. I wonder if this is stable across Python versions and platforms, and etc. python api exception error-handling errno share|improve this question edited Sep 5 '12 at 14:46 Simeon Visser 52.6k877105 asked Sep 5 '12 at 14:08 Anton Daneyko 1,53031634 add a comment| 1 Answer 1 active oldest votes up vote 7 down vote accepted It is better to use values from the errno module instead of hardcoding the value 2: try: shutil.move(old_path, new_path) except IOError as e: if e.errno != errno.ENOENT: raise e This makes your code less likely to break in case the integer error value changes (although that is unlikely to occur). share|improve this answer answered Sep 5 '12 at 14:11 Simeon Visser 52.6k877105 4 "unlikely" is an understatement - the number of programs that would break is mind boggling, it will never happen. But using a symbol rather than a magic number is always preferred. –Mark Ransom Sep 5 '12 at 14:16 Thanks a lot. I did not even know, such a module exists. This is exactly what I wanted. –Anton Daneyko Sep 5 '12 at 15:17 add a comment| Your Answer draft saved draft discarded Sign up or log in Sign up using Google Sign up using Facebook Sign up using Email and Password Post as a guest Name Email Post as a guest Name Email discard By posting your answer, you agree to the privacy policy and terms o