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

### 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.

``````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 */

``````

User Agent is: `Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36`

### Challenge Information:

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

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 =

1 Like

Thank you very much!

1 Like

This topic was automatically closed 182 days after the last reply. New replies are no longer allowed.