undirected_cycle_detect.py

def detect_cycle(node, graph, visited, parent):
    visited.add(node)
    for neigh in graph[node]:
        if neigh not in visited:
            cycle = detect_cycle(neigh, graph, visited, node)
            if cycle == True:
                return True
        else:
            if parent != neigh:
                return True
    return False

if __name__ == "__main__":
    graph = {
        1: [2],
        2: [3],
        3: [4],
        4: [5],
        5: [1]
    }
    visited = set()
    is_cycle = detect_cycle(1, graph, visited, None)
    print(is_cycle)