Find cycles in graph with DFS

DFS_find_cycle.py

def has_cycle(graph):
	visited = set()
	recursion_stack = set()
	
	
	def dfs(node):
		visited.add(node)
		recursion_stack.add(node)
		
		for child in graph[node]:
			print(f"{child} and {recursion_stack}")
			if child not in visited:
				if dfs(child):
					return True
			elif child in recursion_stack:
				return True
		
		recursion_stack.remove(node)
		return False

	first = list(graph.keys())[0]		
	return dfs(first)
	
	

# Example graph as an adjacency list (with a cycle)
graph_with_cycle = {
    'A': ['B', 'C'],
    'B': ['D'],
    'C': ['D'],
    'D': ['A']
}

# Example graph as an adjacency list (acyclic)
graph_acyclic = {
    'A': ['D', 'B', 'C'],
    'B': ['D'],
    'C': ['D'],
    'D': ['F','E'],
    'F': [],
    'E': []
}


print("Has Cycle (Graph with Cycle):", has_cycle(graph_with_cycle))  # Output: True
print("Has Cycle (Acyclic Graph):", has_cycle(graph_acyclic))  # Output: False