pydantic库validator的per参数执行顺序问题

pydantic库的validator装饰器提供了per参数，用于控制校验方法的执行顺序。按照文档描述，将per参数设置为true表示该校验方法在标准校验方法之前执行。

然而，在实践中，设置某个校验方法的per参数为true后，发现其执行顺序并未按照预期在第一位。

问题分析

根据提供的代码示例，可以发现以下问题：

• 校验方法username_alphanumeric被设置为per=true ，但其执行顺序并不是最先执行的。
• 代码中校验方法的定义顺序是：name_must_contain_space、passwords_match、username_alphanumeric。

可能的原因

per参数实际上并不是按照校验方法定义顺序来决定执行顺序。它只影响同一校验方法下的多个子方法的执行顺序。

解决方案

要使username_alphanumeric优先执行，可以将该校验方法定义在其他校验方法之前，如下：

from pydantic import BaseModel, ValidationError, validator



class UserModel(BaseModel):
    name: str
    username: str
    password1:str
    password2: str


    @validator(</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">username</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">)
    </span><span style="color: rgba(0, 0, 255, 1)">def</span><span style="color: rgba(0, 0, 0, 1)"> username_alphanumeric(cls, v,values):
        </span><span style="color: rgba(0, 0, 255, 1)">print</span>(values,<span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">执行顺序优先</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">)
        </span><span style="color: rgba(0, 0, 255, 1)">assert</span> v.isalnum(), <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">must be alphanumeric</span><span style="color: rgba(128, 0, 0, 1)">'</span>
        <span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> v


    @validator(</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">name</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">)
    </span><span style="color: rgba(0, 0, 255, 1)">def</span><span style="color: rgba(0, 0, 0, 1)"> name_must_contain_space(cls, v,values):
        </span><span style="color: rgba(0, 0, 255, 1)">print</span>(values,<span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">name</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">)
        </span><span style="color: rgba(0, 0, 255, 1)">if</span> <span style="color: rgba(128, 0, 0, 1)">'</span> <span style="color: rgba(128, 0, 0, 1)">'</span> <span style="color: rgba(0, 0, 255, 1)">not</span> <span style="color: rgba(0, 0, 255, 1)">in</span><span style="color: rgba(0, 0, 0, 1)"> v:
            </span><span style="color: rgba(0, 0, 255, 1)">raise</span> ValueError(<span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">must contain a space</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">)
        </span><span style="color: rgba(0, 128, 0, 1)">#</span><span style="color: rgba(0, 128, 0, 1)"> print(v.title())</span>
        <span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> v.title()

    @validator(</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">password2</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">)
    </span><span style="color: rgba(0, 0, 255, 1)">def</span><span style="color: rgba(0, 0, 0, 1)"> passwords_match(cls, v, values):
        </span><span style="color: rgba(0, 0, 255, 1)">print</span>(values,<span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">password2</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">)
        </span><span style="color: rgba(0, 0, 255, 1)">if</span> <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">password1</span><span style="color: rgba(128, 0, 0, 1)">'</span> <span style="color: rgba(0, 0, 255, 1)">in</span> values <span style="color: rgba(0, 0, 255, 1)">and</span> v != values[<span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">password1</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">]:
            </span><span style="color: rgba(0, 0, 255, 1)">raise</span> ValueError(<span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">passwords do not match</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">)

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