python - TinyDB 插入失败

Question

我尝试将 Python 对象的 JSON 序列化插入到tinydb中。它工作一次，然后失败。

from tinydb import TinyDB, Query
import json

class Test:
    def __init__(self):
        self.test = "a"

    def to_JSON(self):
        return json.dumps(self, default=lambda o: o.__dict__)

db = TinyDB("test.json")
print(Test().to_JSON)
db.insert(Test().to_JSON())
print("Second insert")
db.insert(Test().to_JSON())

导致

{"test": "a"}
Second insert
Traceback (most recent call last):
  File "test.py", line 15, in <module>
    db.insert(Test().to_JSON())
  File "/usr/lib/python3.4/site-packages/tinydb/database.py", line 287, in insert
    data = self._read()
  File "/usr/lib/python3.4/site-packages/tinydb/database.py", line 248, in _read
    return self._storage.read()
  File "/usr/lib/python3.4/site-packages/tinydb/database.py", line 38, in read
    data[eid] = Element(val, eid)
  File "/usr/lib/python3.4/site-packages/tinydb/database.py", line 20, in __init__
    self.update(value)
ValueError: dictionary update sequence element #0 has length 1; 2 is required

JSON 本身对我来说看起来很有效，那么为什么 tinydb 无法再次插入它呢？

Answer 1

我拿错了。insert() 需要一个 dict 对象，而 json.dumps() 生成一个字符串。

from tinydb import TinyDB, Query
import json

class Test:
    def __init__(self):
        self.test = "a"

    def to_JSON(self):
        return json.loads(json.dumps(self, default=lambda o: o.__dict__))

db = TinyDB("test.json")
db.insert(Test().to_JSON())
print("Second insert")
db.insert(Test().to_JSON())