Learn Algorithm Design by Building a Shortest Path Algorithm - Step 47

Python
1

Tell us what’s happening:

I really lost in this step, I did read the previous topics about this and I realize I was missing the slice syntax, even though after I changed my code it’s still giving me a syntax error back, thanks in advance

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)]
}

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)
    
    while unvisited:
        current = min(unvisited, key=distances.get)
        for node, distance in graph[current]:
            if distance + distances[current] < distances[node]:
                distances[node] = distance + distances[current]

# User Editable Region

                if paths[node][-1] == node:
                    paths[node] = paths[current]
                    else:
                    paths[node].extend(paths[current][:1])  

# User Editable Region

    print(f'Unvisited: {unvisited}\nDistances: {distances}\nPaths: {paths}')
    
#shortest_path(my_graph, 'A')

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Challenge Information:

Learn Algorithm Design by Building a Shortest Path Algorithm - Step 47

2

Can you please share the syntax error?

3

Traceback (most recent call last):
File “main.py”, line 21
else:
^^^^
SyntaxError: invalid syntax

4

Hi @nicobox

Try unindenting the else statement, to match the if statement.

Happy coding

1 Like
5

Thanks! I solved it with your advice but I had to remove the slice syntax too :slight_smile:

1 Like