tree-traversals

Efficient and generic traversals for any Python tree structure with full ancestor paths.

Installation

pip install tree-traversals

Supported Traversal Functions

All traversals:

• Take a starting node and a function to get descendants,
• Return an immutable cowlist stack representing the full path from root to the current node, along with the current node itself.

Usage

# coding=utf-8
from __future__ import print_function
from typing import Dict, List
from tree_traversals import (
    pre_order_dfs,
    post_order_dfs,
    layer_order_bfs
)

# Consider a simple binary tree (as a dict)
# - A
#   - B
#     - D
#     - E
#   - C
#     - F
tree = {
    'A': ['B', 'C'],
    'B': ['D', 'E'],
    'C': ['F'],
    'D': [],
    'E': [],
    'F': []
}  # type: Dict[str, List[str]]


def get_children(n):
    # type: (str) -> List[str]
    return tree[n]


# Then, you can perform any traversal easily:
print("Preorder DFS:")
for path, node in pre_order_dfs('A', get_children):
    print(repr(path), '->', repr(node))
# Preorder DFS:
# COWList([]) -> 'A'
# COWList(['A']) -> 'B'
# COWList(['A', 'B']) -> 'D'
# COWList(['A', 'B']) -> 'E'
# COWList(['A']) -> 'C'
# COWList(['A', 'C']) -> 'F'

print("\nPostorder DFS:")
for path, node in post_order_dfs('A', get_children):
    print(repr(path), '->', repr(node))
# Postorder DFS:
# COWList(['A', 'B']) -> 'D'
# COWList(['A', 'B']) -> 'E'
# COWList(['A']) -> 'B'
# COWList(['A', 'C']) -> 'F'
# COWList(['A']) -> 'C'
# COWList([]) -> 'A

print("\nLayer Order BFS:")
for path, node in layer_order_bfs('A', get_children):
    print(repr(path), '->', repr(node))
# Layer Order BFS
# COWList([]) -> 'A'
# COWList(['A']) -> 'B'
# COWList(['A']) -> 'C'
# COWList(['A', 'B']) -> 'D'
# COWList(['A', 'B']) -> 'E'
# COWList(['A', 'C']) -> 'F'

Motivation

When working with trees, structure is easy - but traversal patterns are often rewritten, customized, and bug-prone. tree-traversals lets you:

• Traverse any tree with a single function and a child-getter.
• Access the full ancestor path at every node.
• Clean up and de-duplicate your recursive tree code.
• Support any tree-shaped data—dicts, lists, ASTs, DOMs, file trees, you name it.

Contributing

Contributions are welcome! Please submit pull requests or open issues on the GitHub repository.

License

This project is licensed under the MIT License.