How do I implement depth-first search in Python?

How do I implement depth-first search in Python?

To implement depth-first search (DFS) in Python, you can use recursion or a stack. Would you like to see an example?

Yes, please show me a recursive example.

Here's a simple recursive DFS implementation:

def dfs(graph, node, visited=None):
    if visited is None:
        visited = set()
    visited.add(node)
    for neighbor in graph[node]:
        if neighbor not in visited:
            dfs(graph, neighbor, visited)
    return visited

This function takes a graph and a starting node.

What does the graph structure look like?

The graph can be represented as a dictionary where keys are nodes and values are lists of neighboring nodes. For example:

graph = {
    'A': ['B', 'C'],
    'B': ['A', 'D', 'E'],
    'C': ['A', 'F'],
    'D': ['B'],
    'E': ['B', 'F'],
    'F': ['C', 'E']
}