Why are Python exceptions named "Error" (e.g. ZeroDivisionError, NameError, TypeError etc) and not "Exception" (e.g. ZeroDivisionException, NameException, TypeException etc).
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 error and exception.
Is there a difference in Python also or not? Can someone explain or point me to some documentation explaining it?
Thank you!
Disclaimer: I don't know exactly. I'd guess its convention - in the sense that an Exception can have any name, and the names are chosen to sound meaningful.
There are even exceptions that are called StopIteration or GeneratorExit. I guess these examples sound more concise than StopIterationException or GeneratorException.
It's just naming. In Java, you have java.lang.Error distinct from other Throwables because those kinds of errors need to be unchecked. In Python, all exceptions are unchecked, so the distinction is kind of pointless.
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.
Python is fairly similar to Java in this respect. But Python's Exception should be compared to Java's Throwable.
As Throwables come in all kinds of flavors, Error, RuntimeException and (checked) Exception, so do Python's (though no checked exceptions).
As for the language, and Error is exceptional, so that inheritance hierarchy is not strange.
I don't particularly like the name Exception though. Exceptions are not only used for exceptional circumstances (like hopefully Errors) but also to just get out of the control flow. Because that is what a Exception does; it jumps out of the normal flow of control to a marked point. A bit like a goto, but more refined.
That said,every time you have a situation in which no suitable return value can be found you tend to use an Exception. Both in Python as in Java.
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).