Learn Algorithm Design by Building a Shortest Path Algorithm - Step 31

[lmoh3479]

Tell us what’s happening:

I have an error: You should use the append() method to append start to paths[start] .

Pretty sure that’s what I did, but I may be misinterpreting.

Your code so far

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

/* User Editable Region */

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}.append(start)
    
    print(f'Unvisited: {unvisited}\nDistances: {distances}')
    
shortest_path(my_graph, 'A')

/* User Editable Region */

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Challenge Information:

Learn Algorithm Design by Building a Shortest Path Algorithm - Step 31

freeCodeCamp.org

[JeremyLT]

@lmoh3479

paths = {node: [] for node in graph}.append(start)

You shouldn’t modify the lines that are already there. You need to append on a separate line.

Here you are appending to the entire paths, not paths[start].

Also, the call to append() doesn’t return the whole paths back - it returns None, so you don’t want the append() on the right hand side of an =

[lmoh3479]

Thank you very much!