使用像networkx这样的网络库可以简化这个问题，你想要的是从根节点和叶节点找到所有的路径。

# pip install networkx
import networkx as nx
import itertools
# Create a directed graph from Pandas edges list
G = nx.from_pandas_edgelist(df, source='OFF', target='ON', create_using=nx.DiGraph)
# Find all roots and leaves
roots = [node for node, degree in G.in_degree if degree == 0]
leaves = [node for node, degree in G.out_degree if degree == 0]
# Get all possible paths between roots and leaves
paths = []
for root, leaf in itertools.product(roots, leaves):
    for path in nx.all_simple_paths(G, root, leaf):
        paths.append(path)

输出：

>>> paths
[['B', 'A', 'C', 'T'], ['D', 'F', 'H']]

可视化：

import matplotlib.pyplot as plt
nx.draw_networkx(G)
plt.show()

输出：