Python获取JSON指定键的父键路径：遇'unhashable type: list'报错求助

Got it, let's work through this problem. You're trying to get the parent key path (like PROJ1/LOB1 when searching for a1) from a JSON structure where all keys inside lists are unique, but the code you found elsewhere throws an unhashable type: 'list' error. Let's break down why that happens and fix it.

Why the Error Happens #

The unhashable type: 'list' error almost always means the original code tried to use a list in a context that requires hashable objects—like using it as a dictionary key or adding it to a set. Since your JSON includes lists, the original code probably didn't handle list traversal correctly, leading it to treat lists as hashable entities (which they aren't).

Solution: Recursive Traversal with List Handling #

Since your lists contain unique keys, we can write a recursive function that traverses both dictionaries and lists, building the path only from dictionary keys (since lists don't contribute to the key path). Here's a working implementation:

def find_parent_key_path(data, target_key, current_path=""):
    # Traverse dictionaries first
    if isinstance(data, dict):
        for key, value in data.items():
            # Build the new path by appending the current dictionary key
            updated_path = f"{current_path}/{key}" if current_path else key
            
            # If we found the target key, return its parent path (the current path before adding this key)
            if key == target_key:
                return current_path
            
            # Recursively search the value for the target key
            result = find_parent_key_path(value, target_key, updated_path)
            if result is not None:
                return result
    
    # Traverse lists by checking each item (lists don't add to the path)
    elif isinstance(data, list):
        for item in data:
            result = find_parent_key_path(item, target_key, current_path)
            if result is not None:
                return result
    
    # If target key not found in this branch
    return None

How to Use It #

Let's test this with a sample JSON structure matching your scenario:

# Example JSON data
sample_data = {
    "PROJ1": {
        "LOB1": {
            "a1": "sample_value",
            "b1": "another_value"
        },
        "LOB2": {
            "a2": "third_value"
        }
    },
    "PROJ2": [
        {"c1": "list_value_1"},
        {"a1": "list_value_2"}  # Unique key in the list, as per your requirement
    ]
}

# Find parent path for "a1"
parent_path = find_parent_key_path(sample_data, "a1")
print(parent_path)  # Output: PROJ1/LOB1

Notes #

• If your target key might appear multiple times in the JSON, modify the function to collect all paths instead of returning the first one. Here's a quick adjustment:

  def find_all_parent_paths(data, target_key, current_path="", paths=None):
      if paths is None:
          paths = []
      
      if isinstance(data, dict):
          for key, value in data.items():
              updated_path = f"{current_path}/{key}" if current_path else key
              if key == target_key:
                  paths.append(current_path)
              find_all_parent_paths(value, target_key, updated_path, paths)
      elif isinstance(data, list):
          for item in data:
              find_all_parent_paths(item, target_key, current_path, paths)
      
      return paths
  

  Calling this with the sample data would return ["PROJ1/LOB1", "PROJ2"] for key a1.

Key Fixes from the Original Code #

• We never treat lists as part of the key path (since they don't have named keys), so we avoid trying to hash them.
• Recursion handles nested dictionaries and lists seamlessly without relying on hashable objects for tracking paths.

内容的提问来源于stack exchange，提问作者Pasha