Python Invalid Input Error
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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 an except python exception message clause that mentions a particular class, that clause also handles any exception classes derived
Python Custom Exception
from that class (but not exception classes from which it is derived). Two exception classes that are not related via subclassing python filenotfounderror 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 python valueerror example 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 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
Python Exception Class Methods
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-defined classes (for that, use Exception). If str() or unicode() 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. New in version 2.5. 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
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 perhaps the most common kind of complaint you python 3 exceptions get while you are still learning Python: >>> while True print('Hello world') File "
Python Attributeerror Object Has No Attribute
earliest point in the line where the error was detected. The error is caused by (or at least detected at) the token preceding the arrow: in the example, the error is detected at the function print(), https://docs.python.org/2/library/exceptions.html 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, 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 https://docs.python.org/3/tutorial/errors.html 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 "
here for a quick overview of the site Help Center Detailed answers to any questions you might have http://stackoverflow.com/questions/256222/which-exception-should-i-raise-on-bad-illegal-argument-combinations-in-python 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 http://crashcourse.housegordon.org/python-exceptions-handling-tips.html 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, python exception just like you, helping each other. Join them; it only takes a minute: Sign up Which exception should I raise on bad/illegal argument combinations in Python? up vote 236 down vote favorite 26 I was wondering about the best practices for indicating invalid argument combinations in Python. I've come across a few situations where you have python invalid input a function like so: def import_to_orm(name, save=False, recurse=False): """ :param name: Name of some external entity to import. :param save: Save the ORM object before returning. :param recurse: Attempt to import associated objects as well. Because you need the original object to have a key to relate to, save must be `True` for recurse to be `True`. :raise BadValueError: If `recurse and not save`. :return: The ORM object. """ pass The only annoyance with this is that every package has its own, usually slightly differing BadValueError. I know that in Java there exists java.lang.IllegalArgumentException -- is it well understood that everybody will be creating their own BadValueErrors in Python or is there another, preferred method? python exception arguments share|improve this question edited Nov 2 '11 at 19:26 sth 128k33204309 asked Nov 1 '08 at 23:02 cdleary 27.4k40130178 add a comment| 4 Answers 4 active oldest votes up vote 245 down vote accepted I would just raise ValueError, unless you need a more specific exception.. def import_
generic Exception. Use user-defined exceptions for application-level errors. Update, 2016-02-26 The kind folks at Webucator made a video based on this post. Check out the video at: https://youtu.be/T94vZmOZodY and other Webucator Online Python Classes. Disclaimer: I’m not a python fan (and certainly not an expert). Comments, feedback, suggestions and improvements are welcomed. without catching exceptions This typical python code: #!/usr/bin/env python import sys a = open("/non/existing/file","r") Will result in this output: $ ./bad0.py Traceback (most recent call last): File "./bad0.py", line 3, in