FAQ: Depth-First Search: Python - The Finishing Touches

Frequently Asked Questions Python FAQ
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This community-built FAQ covers the “The Finishing Touches” exercise from the lesson “Depth-First Search: Python”.

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This exercise can be found in the following Codecademy content:

Computer Science

FAQs on the exercise The Finishing Touches

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In this implementation of depth-first-search, how does the path variable ‘bubble’ up to the previous recursive calls when a value is found?

def dfs(root, target, path=[]):
  path = path + [root]

  if root.value == target:
    print("Value found")
    return path

  for child in root.children:
    node_found = dfs(child, target, path)

    if node_found is not None:
      return node_found

  return None

For example, if this is my tree:
A
├─B
├─D
└─E
└─C
├─F
└─G

Then this is what searching for F might look like:

# -----A------
# path = [A]
#     dfs(child = C, path = [A])
# ----        C---------
#             path = [A,C]
#                  dfs(child = G, path = [A,C])
#                       return None
#                   dfs(child = F, path = [A,C])
#                       ----F------
                        # path = [A,C,F]
#                         return path

Do the outer function calls just pass the path value [A,C,F] back up the stack and don’t finish executing?