Copying trees

[elfring]

I am looking for programming interfaces which support to copy trees while preserving referential integrity.
Further data processing can be performed with such copies.

[jannikmi]

The regular copy() and deepcopy() methods can be used for this.
In my custom node class i have added these functions:

def __copy__(self):
    return self.__class__(
        self.attributes,
    )

def __deepcopy__(self, memodict={}):
    """computes a deep copy of the sub-tree the node is a root of

    ATTENTION: this copy mechanism does only copy the instances from `self` downwards!
    -> call deepcopy(root_node) to copy a full tree
      """
      my_copy = copy(self)
      # recursion towards the leaves
      my_copy.children = [deepcopy(child) for child in self.children]
      return my_copy

It would however be cool if the nodes supported this by default.
With some additional functionality like node.copy_tree() which copies all nodes of the tree but then returns the copy of the node (not the root).

Perhaps this implementation of mine helps:

def copy_my_tree(self) -> "TreeNode":
    """computes a deep copy of the full tree the node belongs to

    Returns: the node corresponding to `self` in the copied tree
    """
    my_root = self.root
    my_root_copy = deepcopy(my_root)  # full copy of my tree
    # find copy of myself based on matching the some argument along the path
    # NOTE: more efficient than searching the whole tree
    matched_node = my_root_copy
    for node in self.path:  # walk down from the root
        if (
            node.is_root
        ):  # skip the first node in the path = root, has been matched already
            continue
        label2match = node.label
        matched_node = anytree.search.find(
            matched_node, lambda n: n.label == label2match
        )
    my_copy = matched_node
    return my_copy