Functions

Recursion

Recursive functions solve nested problems by calling themselves on smaller pieces.

A leaf node is the base case. It has no children, so the function can return its own value without making another recursive call.

Source

def total(node):
    subtotal = node["value"]
    for child in node["children"]:
        subtotal += total(child)
    return subtotal

print(total({"value": 2, "children": []}))

Output

A non-leaf node solves the same problem for each child, then combines those smaller totals with its own value.

Source

tree = {
    "value": 1,
    "children": [
        {"value": 2, "children": []},
        {"value": 3, "children": [{"value": 4, "children": []}]},
    ],
}

print(total(tree))

Output

Notes

Every recursive function needs a base case that stops the calls.
Recursion fits nested data better than flat repetition.
Python limits recursion depth, so loops are often better for very deep or simple repetition.

Run the complete example

Expected output

2
10

Execution time appears here after you run the example.

Recursion

See also

Run the complete example

Example code

Expected output