[Python] How to Validate if a List Matches a Given Structural Pattern?

I am trying to write a Python function to validate whether a given list follows the same structure as a predefined "model" list, which in my particular case is:

model = [
["h", "P12", "P13"],
["P12", "P23", "eL"],
["P13", "P23", "eR"]
]


In words:

• The fixed elements "h", "eL", and "eR" must appear in different sublists.
• The remaining elements (placeholders) - "P12", "P13", and "P23" - are arbitrary elements depending on the given list to test. The order of the elements is irrelevant
• Repetition of the elements "h", "eL", and "eR" in a sublist are allowed if it fits the model structure.

So, for example:

test_list_1 = [
["h", "a2", "a3"],
["a2", "a4", "eL"],
["a3", "a4", "eR"]
]

> True


test_list_2 = [
["h", "h", "Y"],
["h", "Z", "eL"],
["Y", "Z", "eR"]
]

> True


test_list_3 = [
["h", "X", "eL"],
["X", "Z", "eL"],
["eL", "Z", "eR"]
]

> True


test_list_4 = [
["h", "P1", "eL"],
["P1", "P3", "P2"], # ❌ there is no list containing "eL"
["P2", "P3", "eR"]
]

> False


I have tried with ChatGPT, but the following code is not properly working, and so far I cannot make it work:

from collections import defaultdict

def validate_structure(model, test_list):
fixed_elements = {"h", "eL", "eR"}
model_fixed_positions = {}
placeholder_mapping = {}

# Step 1: Identify where fixed elements appear in the model
for i, sublist in enumerate(model):
for item in sublist:
if item in fixed_elements:
model_fixed_positions[item] = i

# Step 2: Identify where fixed elements appear in the test list
test_fixed_positions = {}
for i, sublist in enumerate(test_list):
for item in sublist:
if item in fixed_elements:
if item in test_fixed_positions:
return False # Each fixed element must be in a distinct sublist
test_fixed_positions[item] = i

# Step 3: Ensure fixed elements are in corresponding positions
if set(model_fixed_positions.keys()) != set(test_fixed_positions.keys()):
return False # Missing or extra fixed elements

for key in model_fixed_positions:
if model_fixed_positions[key] != test_fixed_positions[key]:
return False # Fixed elements must appear in the same indexed sublists

# Step 4: Establish and validate placeholder mapping
for i, (model_sublist, test_sublist) in enumerate(zip(model, test_list)):
model_placeholders = [x for x in model_sublist if x not in fixed_elements]
test_placeholders = [x for x in test_sublist if x not in fixed_elements]

if len(model_placeholders) != len(test_placeholders):
return False # Different number of elements

for m_item, t_item in zip(model_placeholders, test_placeholders):
if m_item in placeholder_mapping:
if placeholder_mapping[m_item] != t_item:
return False # Inconsistent placeholder mapping
else:
placeholder_mapping[m_item] = t_item

return True # Structure matches

# Example usage:
print(validate_structure(model, test_list_2)) # Expected: True, but returns False

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