Topological_sort_with_cycle_check.py

def Topological_sort_with_cycle_check(adj):
    visit = {x:0 for x in adj}
    result = []
    def dfs_visit(node):
        if visit[node] == -1:
            return False
        if visit[node] == 1:
            return True
        visit[node] = -1
        for neighbor in adj[node]:
            if dfs_visit(neighbor) == False:
                return False
        visit[node] = 1
        result.insert(0, node)
        return True
    for node in adj:
        if dfs_visit(node) == False:
            return 'Not a DAG'
    return result
adj = {'A':['B','D'], 'B':['C','D'], 'C':[], 'D':['E'], 'E':[]}