英文:
How to set a Pydantic field value depending on other fields
问题
from pydantic import BaseModelclass Grafana(BaseModel):user: strpassword: strhost: strport: strapi_key: str | None = None@propertydef GRAFANA_URL(self):return f"http://{self.user}:{self.password}@{self.host}:{self.port}"API_DATASOURCES = "/api/datasources"API_KEYS = "/api/auth/keys"
英文:
from pydantic import BaseModelclass Grafana(BaseModel):user: strpassword: strhost: strport: strapi_key: str | None = NoneGRAFANA_URL = f"http://{user}:{password}@{host}:{port}"API_DATASOURCES = "/api/datasources"API_KEYS = "/api/auth/keys"
With Pydantic I get two unbound variables error messages for user, password, etc. in GRAFANA_URL.
Is there a way to solve this? In a regular class, I would just create GRAFANA_URL in the __init__ method. With Pydantic, I'm not sure how to proceed.
答案1
得分: 5
Option A: 使用@validator
请查看验证器文档以获取详细信息。
from typing import Anyfrom pydantic import BaseModel, validatorclass Model(BaseModel):foo: strbar: strfoobar: str = ""@validator("foobar", always=True)def set_if_empty(cls, v: str, values: dict[str, Any]) -> str:if v == "":return values["foo"] + values["bar"]return vobj = Model(foo="a", bar="b")print(obj) # foo='a' bar='b' foobar='ab'
这样，foobar仍然是一个常规模型字段。
请注意，为了使此功能正常工作，foobar必须在foo和bar之后定义。否则，您将不得不使用根验证器。
Option B: 将其作为@property
from pydantic import BaseModelclass Model(BaseModel):foo: strbar: str@propertydef foobar(self) -> str:return self.foo + self.barobj = Model(foo="a", bar="b")print(obj) # foo='a' bar='b'print(obj.foobar) # ab
然后foobar将不再是模型字段，因此不会包含在模式中。这可能与您相关或不相关。
Option C: 将其作为@computed_field（仅适用于Pydantic v2！）
定义计算字段将在Pydantic 2中可用。
from pydantic import BaseModel, computed_fieldclass Model(BaseModel):foo: strbar: str@computed_field@propertydef foobar(self) -> str:return self.foo + self.barobj = Model(foo="a", bar="b")print(obj) # foo='a' bar='b' foobar='ab'
英文:
Option A: Use a @validator
See the validators documentation for details.
from typing import Anyfrom pydantic import BaseModel, validatorclass Model(BaseModel):foo: strbar: strfoobar: str = ""@validator("foobar", always=True)def set_if_empty(cls, v: str, values: dict[str, Any]) -> str:if v == "":return values["foo"] + values["bar"]return vobj = Model(foo="a", bar="b")print(obj) # foo='a' bar='b' foobar='ab'
That way foobar remains a regular model field.
Note that for this to work, foobar must be defined after foo and bar. Otherwise you will have to use a root validator.
Option B: Make it a @property
from pydantic import BaseModelclass Model(BaseModel):foo: strbar: str@propertydef foobar(self) -> str:return self.foo + self.barobj = Model(foo="a", bar="b")print(obj) # foo='a' bar='b'print(obj.foobar) # ab
Then foobar will not be a model field anymore and therefore not part of the schema. That may or may not be relevant to you.
Option C: Make it a @computed_field (Pydantic v2 only!)
Defining computed fields will be available for Pydantic 2.
from pydantic import BaseModel, computed_fieldclass Model(BaseModel):foo: strbar: str@computed_field@propertydef foobar(self) -> str:return self.foo + self.barobj = Model(foo="a", bar="b")print(obj) # foo='a' bar='b' foobar='ab'
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