Structure¶
Tree
objects define a tree structure by implementing the local movement methods
Each of which takes and returns a position object of arbitrary type (fixed for the Tree)
as done in urwids ListWalker API. Apart from this, a Tree is assumed to define a dedicated
position tree.root that is used as fallback initially focussed element,
and define the __getitem__()
method to return its content (usually a Widget) for a given position.
Note that Tree
only defines a tree structure, it does not necessarily have any decoration around
its contained Widgets.
There is a ready made subclass called SimpleTree
that offers the tree API for a given
nested tuple structure. If you write your own classes its a good idea to subclass Tree
and just overwrite the above mentioned methods as the base class already offers a number of
derivative methods.
API¶
-
class
urwidtrees.tree.
Tree
[source]¶ Base class for a tree strucures that can be displayed by
TreeBox
widgets. An instance defines a structure by defining local transformations on positions. That is, by overwriting- next_sibling_position
- prev_sibling_position
- parent_position
- first_child_position
- last_child_position
that compute the next position in the respective direction. Also, they need to implement method __getitem__ that returns a
Widget
for a given position.The type of objects used as positions may vary in subclasses and is deliberately unspecified for the base class.
This base class already implements methods based on the local transformations above. These include
depth()
,last_decendant()
and[next|prev]_position
that computes next/previous positions in depth-first order.-
first_ancestor
(pos)[source]¶ position of pos’s ancestor with depth 0. Usually, this should return the root node, but a
Tree
might represent a forrest - have multiple nodes without parent.
-
first_child_position
(pos)[source]¶ returns the position of the first child of the node at pos, or None if none exists.
-
last_child_position
(pos)[source]¶ returns the position of the last child of the node at pos, or None if none exists.
-
next_sibling_position
(pos)[source]¶ returns the position of the next sibling of the node at pos, or None if none exists.
-
class
urwidtrees.tree.
SimpleTree
(treelist)[source]¶ Walks on a given fixed acyclic structure given as a list of nodes; every node is a tuple (content, children), where content is a urwid.Widget to be displayed at that position and children is either None or a list of nodes.
Positions are lists of integers determining a path from the root node with position (0,).
-
first_child_position
(pos)[source]¶ returns the position of the first child of the node at pos, or None if none exists.
-