如何对含公共键的嵌套字典列表按键值求和合并？

The problem with using Counter directly on the top-level dictionaries is that it replaces existing values instead of handling the nested key-value sums. Since your data has two levels of nesting, we need to apply Counter to the inner dictionaries to correctly accumulate the values.

Here's a working solution:

from collections import Counter

ps = [{'one': {'a': 30, "b": 30}, 'two': {'a': -1000}}, {'three': {'a': 44}, 'one': {'a': -225}}, {'one': {'a': 2000, "b": 30}}]

merged = {}

# Iterate through each dictionary in the list
for item in ps:
    # Process each top-level key and its nested dictionary
    for top_key, inner_dict in item.items():
        # Initialize the top-level key with a Counter if it doesn't exist
        if top_key not in merged:
            merged[top_key] = Counter(inner_dict)
        else:
            # Update the existing Counter with the new inner dictionary values (sums them)
            merged[top_key].update(Counter(inner_dict))

# Convert inner Counters back to regular dictionaries for the final result
result = {key: dict(counter) for key, counter in merged.items()}

print(result)

How this works: #

• We start with an empty merged dictionary to build our result.
• For each dictionary in the input list, we loop through its top-level keys (like one, two).
• For each top-level key, we use Counter on the inner dictionary:
  • If the key isn't in merged, we add it with a Counter of the inner dict.
  • If it is present, we call update() on the existing Counter, which automatically sums the values for matching inner keys (like a or b).
• Finally, we convert the inner Counters back to regular dictionaries to match your desired output format.

Running this code will produce exactly the nested dictionary you want:

{"one": {"a": 1805, "b": 60}, "two": {"a": -1000}, "three": {"a": 44}}

内容的提问来源于stack exchange，提问作者Alex