Please help me interpret a piece of divine Python code, thank you! !

Question

def combine_dicts(a, b):
    if b is None:
        return a
    return dict(a.items() + b.items() +
                [(k, combine_dicts(a[k], b[k])) for k in set(b) & set(a)])

a and b should both be dict type data. How to understand this function, especially the last return? ?

Answer 1

This is how it is written in Python 2. Come to Python version 3.6:

def dict_deep_merge(a, b):
  if not b:
    return a
  return {**a, **b,
    **{k: dict_deep_merge(a[k], b[k])
       for k in set(a) & set(b)}}

It should be more efficient. Everything else is pretty much the same.

It’s not a god-level code, nor is it difficult to understand. Just recursively merge values ​​with the same key. What you need to know:

• dict’s items method

Addition of

• tuples

• Gathering together

• The meaning of dict parameters

Answer 2

函数的作用合并两个dict
比如
a = {'a': {'A': 1}, 'b': 1}
b = {'a': {'B': 1}}
合并成
{'a': {'A': 1, 'B': 1}, 'b': 1}

set(b) & set(a)是取a,c的key交集，如上a,b的key交集为a, 再递归运行子dict

Answer 3

Ask a question, is there something wrong with the code? If the value in the same key is a string, will the items function report an error?