distances = {
    'A': {'B': 5},
    'B': {'C': 10},
    'C': { 'D': 50, 'F': 1},
    'D': {},
    'F': {'B': 2},
}


def dixstra(graph,start,end):
    unvisited ={ i: float("inf") for i in graph}
    visited = dict()
    node= start
    unvisited[node] = 0
    while True:
        for neighbour, distance in graph[node].items():
            if neighbour not in unvisited: continue
            new_distance = distance + unvisited[node]
            if unvisited[neighbour] > new_distance:
                unvisited[neighbour] = new_distance
        visited[node]= unvisited[node]
        if node == end: break
        del unvisited[node]
        if not unvisited: break
        node = next_node(unvisited)
    return visited


def next_node(costs):
    lowest_cost = float('inf')
    lowest_cost_node = None
    for node in costs:
        if costs[node] < lowest_cost :
            lowest_cost = costs[node]
            lowest_cost_node= node

    return lowest_cost_node


print(dixstra(distances,"A","D"))