Functions to extract for a xgboost forest for each tree and each leaf - the middle nodes that create the path to reach it.

xgboost_leaf_paths_extractor.py

def _root_to_leaf_route(df, stack, routes):
    current_node = df.loc[df.Node == stack[-1]]
    if current_node.Feature.values[0] == 'Leaf':
        routes[current_node.Node.values[0]] = list(stack)
        stack.pop()
        return
    stack.append(int(current_node.Yes.values[0].split('-')[1]))
    _root_to_leaf_route(df, stack, routes)
    stack.append(int(current_node.No.values[0].split('-')[1]))
    _root_to_leaf_route(df, stack, routes)
    stack.pop()
    return
  
def extract_root_to_leaf_routes_for_forest(xgb):
    routes_forest = {}
    for i in range(len(xgb.get_booster().get_dump())):
        routes_forest[i] = extract_root_to_leaf_routes_for_tree(xgb, i)
    return routes_forest
  
def extract_root_to_leaf_routes_for_tree(xgb, tree_index):
    df = xgb.get_booster().trees_to_dataframe()
    df = df.loc[df.Tree == tree_index].set_index('ID')
    routes = {}
    stack = [0]
    _root_to_leaf_route(df, stack, routes)
    return routes