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[英]How to use pydantic models in subclass with graphene-pydantic and graphene in python?
[英]Pydantic - How to subclass a builtin type
我正在嘗試創建一個期望接收毫秒而不是秒的 timedelta 子類,但它目前無法正常工作。
我是在反對谷物嗎? Pydantic 是否有“正確”的方法來實現這一目標? 或者我是否需要以某種方式告訴 Pydantic MillisecondTimedelta
只是一個timedelta
..
from datetime import timedelta
from pydantic import BaseModel
class MillisecondTimedelta(timedelta):
@classmethod
def __get_validators__(cls):
# timedelta expects seconds
yield lambda v: v / 1000
yield cls
class MyModel(BaseModel):
td: MillisecondTimedelta
data = {
"td": 7598040,
}
print(MyModel(**data))
結果是:
Traceback (most recent call last):
File "main.py", line 14, in <module>
class MyModel(BaseModel):
File "pydantic/main.py", line 262, in pydantic.main.ModelMetaclass.__new__
File "pydantic/fields.py", line 315, in pydantic.fields.ModelField.infer
File "pydantic/fields.py", line 284, in pydantic.fields.ModelField.__init__
File "pydantic/fields.py", line 362, in pydantic.fields.ModelField.prepare
File "pydantic/fields.py", line 541, in pydantic.fields.ModelField.populate_validators
File "pydantic/class_validators.py", line 255, in pydantic.class_validators.prep_validators
File "pydantic/class_validators.py", line 238, in pydantic.class_validators.make_generic_validator
File "/usr/lib/python3.8/inspect.py", line 3105, in signature
return Signature.from_callable(obj, follow_wrapped=follow_wrapped)
File "/usr/lib/python3.8/inspect.py", line 2854, in from_callable
return _signature_from_callable(obj, sigcls=cls,
File "/usr/lib/python3.8/inspect.py", line 2384, in _signature_from_callable
raise ValueError(
ValueError: no signature found for builtin type <class '__main__.MillisecondTimedelta'>
如__get_validators__()
的文檔頁面所示,您需要生成一個或多個驗證器。
修改后的 class 報道如下; 問題是 Pydantic 理解(對於 timedelta 字段) int 並浮動為 seconds(source) 。
class MillisecondTimedelta(timedelta):
@classmethod
def __get_validators__(cls):
yield cls.validate
@classmethod
def validate(cls, v):
if any(isinstance(v, t) for t in (int, float)):
return cls(milliseconds=v)
現在一切都應該正常工作。
>>> data = {"td": 1000}
>>> print(MyModel(**data))
td=MillisecondTimedelta(seconds=1)
編輯:如果沒有自定義 class 和驗證器,可以使用 function 編輯要分配給 class 構造函數的值; 需要裝飾這個 function,如圖所示
class MyModel(BaseModel):
td: timedelta
@validator('td')
def convert_to_ms(cls, v):
return v / 1000
此解決方案也有效:
>>> data = {"td": 3000}
>>> print(MyModel(**data))
td=datetime.timedelta(seconds=3)
啊哈,原來我需要改變兩件事。
實際上從驗證器返回一個timedelta
,我返回的是我的自定義子類cls
。
不要子類timedelta
from datetime import timedelta
from pydantic import BaseModel
class MillisecondTimedelta:
@classmethod
def __get_validators__(cls):
yield lambda v: timedelta(milliseconds=v)
class MyModel(BaseModel):
td: MillisecondTimedelta
data = {
"td": 7598040,
}
print(repr(MyModel(**data)))
MyModel(td=datetime.timedelta(seconds=7598, microseconds=40000))
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