Inheritance structure of the various "LT" objects (https://github.com/euske/pdfminer/blob/master/pdfminer/layout.py)

lt_structure.py

# -*- coding: utf-8 -*-

from inspect import isclass
from pdfminer import layout


class _LTNode(object):

    __singletons = {}

    def __new__(cls, lt_class):
        if lt_class in cls.__singletons:
            return cls.__singletons[lt_class]
        self = super(_LTNode, cls).__new__(cls)
        self.lt_class = lt_class
        self._subs = []
        cls.__singletons[lt_class] = self
        for parent_lt_class in self.lt_class.__bases__:
            if parent_lt_class is object:
                continue
            parent_node = _LTNode(parent_lt_class)
            parent_node.append(self)
        return self

    def is_top(self):
        return self.lt_class.__bases__ == (object,)

    def append(self, node):
        self._subs.append(node)

    def print_tree(self, offset_string=''):
        lt_name = self.lt_class.__name__
        lt_name_len = len(lt_name)
        offset_string += (' ' * (lt_name_len / 2))
        print lt_name
        subs_len = len(self._subs)
        for idx, sub in enumerate(self._subs):
            print offset_string + '|'
            print offset_string + '|'
            print offset_string + '+---',
            sub.print_tree(offset_string + ('    '
                                            if idx + 1 == subs_len
                                            else '|   '))


def main():
    top_nodes = []
    for key in dir(layout):
        if not key.startswith('LT'):
            continue
        lt_class = getattr(layout, key)
        if not isclass(lt_class):
            continue
        node = _LTNode(lt_class)
        if node.is_top():
            top_nodes.append(node)
    for top_node in top_nodes:
        top_node.print_tree()
        print
        print


if __name__ == '__main__':
    main()

lt_structure.txt

LTItem
   |
   |
   +--- LTAnno
   |
   |
   +--- LTComponent
            |
            |
            +--- LTChar
            |
            |
            +--- LTContainer
            |        |
            |        |
            |        +--- LTExpandableContainer
            |        |             |
            |        |             |
            |        |             +--- LTTextContainer
            |        |                        |
            |        |                        |
            |        |                        +--- LTTextBox
            |        |                        |       |
            |        |                        |       |
            |        |                        |       +--- LTTextBoxHorizontal
            |        |                        |       |
            |        |                        |       |
            |        |                        |       +--- LTTextBoxVertical
            |        |                        |
            |        |                        |
            |        |                        +--- LTTextGroup
            |        |                        |        |
            |        |                        |        |
            |        |                        |        +--- LTTextGroupLRTB
            |        |                        |        |
            |        |                        |        |
            |        |                        |        +--- LTTextGroupTBRL
            |        |                        |
            |        |                        |
            |        |                        +--- LTTextLine
            |        |                                 |
            |        |                                 |
            |        |                                 +--- LTTextLineHorizontal
            |        |                                 |
            |        |                                 |
            |        |                                 +--- LTTextLineVertical
            |        |
            |        |
            |        +--- LTLayoutContainer
            |                    |
            |                    |
            |                    +--- LTFigure
            |                    |
            |                    |
            |                    +--- LTPage
            |
            |
            +--- LTCurve
            |      |
            |      |
            |      +--- LTLine
            |      |
            |      |
            |      +--- LTRect
            |
            |
            +--- LTImage


LTText
   |
   |
   +--- LTAnno
   |
   |
   +--- LTChar
   |
   |
   +--- LTTextContainer
              |
              |
              +--- LTTextBox
              |       |
              |       |
              |       +--- LTTextBoxHorizontal
              |       |
              |       |
              |       +--- LTTextBoxVertical
              |
              |
              +--- LTTextGroup
              |        |
              |        |
              |        +--- LTTextGroupLRTB
              |        |
              |        |
              |        +--- LTTextGroupTBRL
              |
              |
              +--- LTTextLine
                       |
                       |
                       +--- LTTextLineHorizontal
                       |
                       |
                       +--- LTTextLineVertical

Well there're some multiple inheritance cases this simple script could not properly handle. For example LTAnno is inherited from both LTText and LTItem, or LTChar is inherited from LTComponent and LTText. Also there are mro sequence behind the inheritance.