How to Sorted and display the Subclasses of BaseException

[buran]

about the 'str' in key ... how does it work ? does it mean the key = str will take each element and change them to str type data and compare them ?

yes, I think it's pretty clear from the docs I quoted in my answer. It will apply function supplied as key on each element in the list and use the result to compare/order the element, in this case the function is str() - a built-in function, in the @Gribouillis example - a lambda function (that is anonymous function) which takes one argument klass (i.e. one element) and returns klass.__name__ attribute (which is also a string).