Python Value Error Exception
Contents |
This module never needs to be imported explicitly: the exceptions are provided in the built-in namespace as well as the exceptions module. For class exceptions, in a try statement with
Python Custom Exception
an except clause that mentions a particular class, that clause also handles any exception classes derived python raise valueerror from that class (but not exception classes from which it is derived). Two exception classes that are not related via subclassing are never equivalent, even if they python filenotfounderror have the same name. The built-in exceptions listed below can be generated by 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 containing several items of information (e.g., an error code and a string explaining the
Python Exception Stack Trace
code). The associated value is the second argument to the raise statement. If the exception class is derived from the standard root class BaseException, the associated value is present as the exception instance's args attribute. 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 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. The following exceptions are only used as base classes for other exceptions. exception BaseException¶ The base class for all built-in exceptions. It is not meant to be directly inherited by user-
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 python exception class methods errors, are perhaps the most common kind of complaint you get while you python errno are still learning Python: >>> while True print 'Hello world' File "
Python Attributeerror Object Has No Attribute
^ SyntaxError: invalid syntax The parser repeats the offending line and displays a little ‘arrow' pointing at the earliest point in the line where the error was detected. The error is caused https://docs.python.org/2/library/exceptions.html by (or at least detected at) the token preceding the arrow: in the example, the error is detected at the keyword print, since a colon (':') is missing before it. File name and line number are printed so you know where to look in case the input came from a script. 8.2. Exceptions¶ Even if a statement or expression is syntactically correct, https://docs.python.org/2.7/tutorial/errors.html it may cause an error when an attempt is made to execute it. Errors detected during execution are called exceptions and are not unconditionally fatal: you will soon learn how to handle them in Python programs. Most exceptions are not handled by programs, however, and result in error messages as shown here: >>> 10 * (1/0) Traceback (most recent call last): File "
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 from which it is derived). Two exception classes https://docs.python.org/3.1/library/exceptions.html that are not related via subclassing are never equivalent, even if they have the same name. The built-in exceptions listed below can be generated by 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 (e.g., an error code and a string explaining the code). The python exception 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 raising an inappropriate error. The built-in exception classes can be sub-classed to define python value error new exceptions; programmers are encouraged to at least derive new exceptions from the Exception class and not BaseException. More information on defining exceptions is available in the Python Tutorial under User-defined Exceptions. The following exceptions are used mostly as base classes for other exceptions. exception BaseException¶ The base class for all built-in exceptions. It is not meant to be directly inherited by user-defined classes (for that, use Exception). If bytes() or str() is called on an instance of this class, the representation of the argument(s) to the instance are returned, or the empty string when there were no arguments. args¶ The tuple of arguments given to the exception constructor. Some built-in exceptions (like IOError) expect a certain number of arguments and assign a special meaning to the elements of this tuple, while others are usually called only with a single string giving an error message. with_traceback(tb)¶ This method sets tb as the new traceback for the exception and returns the exception object. It is usually used in exception handling code like this: try: ... except SomeException: tb = sys.exc_info()[2] raise OtherException(...).with_traceback(tb) exception Exception¶ All built-in, non-system-exiting exceptions are derived from this class. All user-defined exceptions should also be derived from this class. exception Ar