Topological_sort.py

def Topological_sort(adj):
    result = []
    def dfs_visit(node):
        for neighbor in adj[node]:
            if neighbor not in seen:
                seen.add(neighbor)
                dfs_visit(neighbor)
        result.insert(0, node) # insert to beginning of list
    seen = set()
    values = []
    [values.extend(v) for v in adj.values()]
    for node in adj:
        if node not in values:
            if node not in seen:
                dfs_visit(node)
    return result
adj = {'A':['B','D'], 'B':['C','D'], 'C':[], 'D':['E'], 'E':[]}