Print the Python Exception/Error Hierarchy

Question

Is the any command line option in python to print the Exception/Error Class hierarchy?

The output should be similar to http://docs.python.org/2/library/exceptions.ht

Answer 1

Reuse code from the standard library instead of rolling your own.

import inspect
import pydoc

def print_class_hierarchy(classes=()):
    td = pydoc.TextDoc()
    tree_list_of_lists = inspect.getclasstree(classes)
    print(td.formattree(tree_list_of_lists, 'NameSpaceName'))

To use this, we need a hierarchy of classes, in the form of a list, that makes sense for us to pass our function. We can build this by recursively searching a classes .__subclasses__() method results, using this function (which I'll keep the canonical version of here):

def get_subclasses(cls):
    """returns all subclasses of argument, cls"""
    if issubclass(cls, type): # not a bound method
        subclasses = cls.__subclasses__(cls)
    else:
        subclasses = cls.__subclasses__()
    for subclass in subclasses:
        subclasses.extend(get_subclasses(subclass))
    return subclasses

Put this together:

list_of_classes = get_subclasses(int)
print_class_hierarchy(list_of_classes)

Which prints (in Python 3):

>>> print_class_hierarchy(classes)
builtins.int(builtins.object)
    builtins.bool
    enum.IntEnum(builtins.int, enum.Enum)
        inspect._ParameterKind
        signal.Handlers
        signal.Signals
    enum.IntFlag(builtins.int, enum.Flag)
        re.RegexFlag
    sre_constants._NamedIntConstant
    subprocess.Handle
enum.Enum(builtins.object)
    enum.IntEnum(builtins.int, enum.Enum)
        inspect._ParameterKind
        signal.Handlers
        signal.Signals
enum.Flag(enum.Enum)
    enum.IntFlag(builtins.int, enum.Flag)
        re.RegexFlag

This gives us a tree of all subclasses, as well as related multiple inheritance classes - and tells us the modules they live in.