python - 读取 JSON 并将键转换为 int

Question

众所周知，json 将 dict 的整数键转换为字符串:

import json
print json.dumps({1: [2.5, 2.5, 2.5], 2: [3, 3, 3, 3]})
# {"1": [2.5, 2.5, 2.5], "2": [3, 3, 3, 3]}

加载回来时恢复整数键最干净的方法是什么？

d = json.loads('{"1": [2.5, 2.5, 2.5], "2": [3, 3, 3, 3]}')
print d
# {u'1': [2.5, 2.5, 2.5], u'2': [3, 3, 3, 3]}

我在想:

d = {int(k): d[k] for k in d}

但是有没有更简洁的方法来处理带有 JSON/Python 整数键的字典，而不需要事后进行键转换？

Answer 1

使用object_hook定义自定义函数并执行操作:

import json

def keystoint(x):
    return {int(k): v for k, v in x.items()}

j = json.dumps({1: [2.5, 2.5, 2.5], 2: [3, 3, 3, 3]})
# {"1": [2.5, 2.5, 2.5], "2": [3, 3, 3, 3]}

print(json.loads(j, object_hook=keystoint))
# {1: [2.5, 2.5, 2.5], 2: [3, 3, 3, 3]}

来自 docs :

object_hook is an optional function that will be called with the result of any object literal decoded (a dict). The return value of object_hook will be used instead of the dict.

---

或者，您也可以使用 object_pairs_hook 来迭代对并保存 .items() 调用(感谢@chepner):

import json

def keystoint(x):
    return {int(k): v for k, v in x}

j = json.dumps({1: [2.5, 2.5, 2.5], 2: [3, 3, 3, 3]})
# {"1": [2.5, 2.5, 2.5], "2": [3, 3, 3, 3]}

print(json.loads(j, object_pairs_hook=keystoint))
# {1: [2.5, 2.5, 2.5], 2: [3, 3, 3, 3]}

来自文档:

object_pairs_hook is an optional function that will be called with the result of any object literal decoded with an ordered list of pairs. The return value of object_pairs_hook will be used instead of the dict.