Skip to content

Find All Leaf Nodes

Zero-dependency Python snippets for finding all leaf nodes in a tree using the standard library.

4 snippets available in this sub-category.

Simple

Leaf nodes in general tree (recursive)

tree leaf find recursive data-structures

Find all leaf nodes in a general tree

def find_leaves(tree):
    leaves = []
    for node, children in tree.items():
        if not children:
            leaves.append(node)
        else:
            leaves.extend(find_leaves(children))
    return leaves


tree = {"A": {"B": {}, "C": {"D": {}, "E": {}}}}
print(find_leaves(tree))  # ['B', 'D', 'E']

Notes

  • Leaf = node with no children (empty dict)

Leaf nodes in binary tree (recursive)

tree binary leaf find recursive data-structures

Find all leaf nodes in a binary tree

def binary_leaves(node):
    if not node:
        return []
    if not node["left"] and not node["right"]:
        return [node["val"]]
    return binary_leaves(node["left"]) + binary_leaves(node["right"])


btree = {
    "val": "A",
    "left": {"val": "B", "left": None, "right": None},
    "right": {
        "val": "C",
        "left": {"val": "D", "left": None, "right": None},
        "right": {"val": "E", "left": None, "right": None},
    },
}
print(binary_leaves(btree))  # ['B', 'D', 'E']

Notes

  • Leaf = node with no left or right child

Complex

Leaf nodes in general tree (iterative, DFS)

tree leaf dfs iterative data-structures

Iterative DFS to find all leaf nodes

def find_leaves_iterative(tree):
    stack = [tree]
    leaves = []
    while stack:
        current = stack.pop()
        for node, children in current.items():
            if not children:
                leaves.append(node)
            else:
                stack.append(children)
    return leaves


tree = {"A": {"B": {}, "C": {"D": {}, "E": {}}}}
print(find_leaves_iterative(tree))  # ['B', 'D', 'E']

Notes

  • Useful for very deep trees (avoids recursion limit)

Edge cases: empty tree, single node

tree leaf edge-case data-structures

Handle edge cases for leaf finding

def find_leaves(tree):
    # Function is defined in one of the above code block
    pass


print(find_leaves({}))  # []
print(find_leaves({"A": {}}))  # ['A']

Notes

  • No leaves in empty tree, root is leaf if no children

🔗 Cross Reference

🏷️ Tags

tree, leaf, dfs, recursive, iterative, edge-case, data-structures

📝 Notes

  • Leaf finding is useful for pruning, summarizing, and more
  • Use iterative methods for very deep trees