Python Error Exception Difference
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you have probably seen some. There are (at least) two distinguishable kinds of errors: syntax errors and exceptions. 8.1. Syntax Errors¶ Syntax errors, python exception class also known as parsing errors, are perhaps the most common kind of python exception message complaint you get while you are still learning Python: >>> while True print('Hello world') File "
Syntax For Generic Except Clause In Python
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(), 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 python print exception 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 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 "
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Is Nested Try Block Possible In Python
like you, helping each other. Join them; it only takes a minute: Sign up Why are Python exceptions named “Error”? up vote 43 down vote favorite 8 Why are Python exceptions named "Error" (e.g. ZeroDivisionError, NameError, TypeError) and https://docs.python.org/3/tutorial/errors.html not "Exception" (e.g. ZeroDivisionException, NameException, TypeException). I come from a Java background and started to learn Python recently, as such this is confusing because in Java there is a distinction between errors and exceptions. Is there a difference in Python also or not? java python exception share|improve this question edited Jul 5 '15 at 14:57 Mark Amery 24.2k12119151 asked May 25 '10 at 10:36 Elena 21933 add a comment| 5 Answers 5 active oldest votes http://stackoverflow.com/questions/2903827/why-are-python-exceptions-named-error up vote 52 down vote You don't name each class with 'Class' in name and each variable with '_variable' in name. The same name you don't name exception using the word 'Exception'. The name should tell something about the meaning of the object. 'Error' is the meaning of most of the exceptions. Not all Exceptions are Errors. SystemExit, KeyboardInterrupt, StopIteration, GeneratorExit are all exceptions and not errors. The word 'Error' in actual errors shows the difference. 'Error' is shorter than 'Exception'. Than can save a few characters in the code width with no loss in meaning. That makes some difference. share|improve this answer answered May 25 '10 at 10:58 Jacek Konieczny 5,1971528 1 Not all Exceptions are Errors: Indeed, there are a number of exceptions that derive from an exception class named Warning. Please see my answer. –DavidRR Mar 10 '15 at 18:52 This is a great visualization docs.python.org/2/library/exceptions.html#exception-hierarchy –Jason Capriotti Apr 12 at 20:43 add a comment| up vote 29 down vote I believe this convention comes from PEP 8 - Style Guide for Python Code: Exception Names Because exceptions should be classes, the class naming convention applies here. However, you should use the suffix "Error" on your exception names (if the exception actually is an error). share|improve this answer edited Jul 5 '15 at 14:59 Mark Amery
Cleaner Python: Use Exceptions Many programmers have had it drilled into their head that exceptions, in any language, should only be used in truly exceptional cases. They're wrong. The Python community's approach to exceptions leads to cleaner code that's https://jeffknupp.com/blog/2013/02/06/write-cleaner-python-use-exceptions/ easier to read. And that's without the monstrous hit to performance commonly associated with exceptions in other languages. EDIT: Updated with more useful exception idioms Using exceptions to write cleaner code? When I talk about "using exceptions", I'm specifically not referring to creating some crazy exception hierarchy for your package and raising exceptions at every possible opportunity. That will most certainly lead to unmaintainable and difficult to understand code. This notion has python exception been widely discussed and is well summarized on Joel Spolsky's blog. Note: Python avoids much of the tension of the "error codes vs exceptions" argument. Between the ability to return multiple values from a function and the ability to return values of different types (e.g. None or something similar in the error case) the argument is moot. But this is besides the point. The style of exception usage I'm advocating is quite python error exception different. In short: take advantage of Python built-ins and standard library modules that already throw exceptions. Exceptions are built in to Python at the lowest levels. In fact, I guarantee your code is already using exceptions, even if not explicitly. Intermezzo: How the for statement works Any time you use for to iterate over an iterable (basically, all sequence types and anything that defines __iter__() or __getitem__()), it needs to know when to stop iterating. Take a look at the code below: words = ['exceptions', 'are', 'useful'] for word in words: print(word) How does for know when it's reached the last element in words and should stop trying to get more items? The answer may surprise you: the list raises a StopIteration exception. In fact, all iterables follow this pattern. When a for statement is first evaluated, it calls iter() on the object being iterated over. This creates an iterator for the object, capable of returning the contents of the object in sequence. For the call to iter() to succeed, the object must either support the iteration protocol (by defining __iter__()) or the sequence protocol (by defining __getitem__()). As it happens, both the __iter__() and __getitem__() functions are required to raise an exception when the items to iterate over are exhausted. __iter__() raises t