freeCodeCamp/curriculum/challenges/german/07-scientific-computing-with-python/learn-algorithm-design-by-building-a-shortest-path-algorithm/65578d4fc3afc3b8f554c882.md

id, title, challengeType, dashedName

id	title	challengeType	dashedName
65578d4fc3afc3b8f554c882	Step 41	20	step-41

--description--

min() takes also a keyword-only argument. Passing a function as an additional argument to min(), you can modify the way the list items are compared.

The result of the line you've just written in the previous step is the node that comes first in alphabetical order. Instead you want to select the unvisited node having the smallest distance from the starting node.

Pass key=distances.get as the second argument to your min() call. In this way, the comparison will take place depending on the value each unvisited list item has inside the distances dictionary.

--hints--

You should pass key=distances.get as the second argument to your min() call.

({ test: () =>  {
    const shortest = __helpers.python.getDef(code, "shortest_path");
    const {function_body} = shortest;    
    assert(function_body.match(/^(\s{4})while\s+unvisited\s*:\s*^\1\1current\s*=\s*min\s*\(\s*unvisited\s*,\s*key\s*=\s*distances\.get\s*\)/ms));
  }
})

--seed--

--seed-contents--

my_graph = {
    'A': [('B', 3), ('D', 1)],
    'B': [('A', 3), ('C', 4)],
    'C': [('B', 4), ('D', 7)],
    'D': [('A', 1), ('C', 7)]
}

def shortest_path(graph, start):
    unvisited = list(graph)
    distances = {node: 0 if node == start else float('inf') for node in graph}
    paths = {node: [] for node in graph}
    paths[start].append(start)
--fcc-editable-region--    
    while unvisited:
        current = min(unvisited)
--fcc-editable-region--    
    print(f'Unvisited: {unvisited}\nDistances: {distances}\nPaths: {paths}')

#shortest_path(my_graph, 'A')