FastAPI从入门到实战（5）——查询参数与字符串校验

- 日理万妓 2024-03-31 12:29 72阅读 0赞

> 本文主要记录查询参数的传递、特性以及字符串类型的数据校验相关内容

### 查询参数 ###

@app02.get("/stu02/query")
    def stu02_query(query: float = 0.01):
        return {
        "query":query}

> 声明不属于路径参数的其他函数参数时，它自动解释为"查询字符串"参数

![image-20221125111609466][]

### 可选参数 ###

@app02.get("/stu02/query/select")
    def stu02_query_select(string: Optional[float] = None,number:int = 1,optionalfloat:float = 6.33):
        return {
        "String":string,"Number":number,"optionalfloat":optionalfloat}

> 声明参数的时候给定默认值，即会解析为选填的参数

![image-20221125111735046][]

### 类型转换 ###

@app02.get("/stu02/query/bool")
    def stu02_type_conversion(
            query:bool = False
    ):
        return {
        "布尔值":query}

> 该请求`FastAPI`会自动将传递的参数转为`bool`类型，当不能够转换的时候将会抛出错误；
> 
> 能转换的如：false、FALSE、0、YES、off

*  http://127.0.0.1:8000/test/stu02/query/bool?query=query

{
        
        "detail": [
            {
        
                "loc": [
                    "query",
                    "query"
                ],
                "msg": "value could not be parsed to a boolean",
                "type": "type_error.bool"
            }
        ]
    }

*  http://127.0.0.1:8000/test/stu02/query/bool?query=off

{
        
        "布尔值": false
    }

*  http://127.0.0.1:8000/test/stu02/query/bool?query=YES

{
        
        "布尔值": true
    }

*  http://127.0.0.1:8000/test/stu02/query/bool?query=1

{
        
        "布尔值": true
    }

### 使用Query默认值 ###

> 声明`Query`即可使用`FastAPI`的`Query`进行数据的校验以及使用更多的元数据；

@app02.get("/stu02/query/default")
    def stu02_query_QueryDefault(param:str = Query(default="QueryDefault")):
        return {
        "DefaultQuery":param}

> 设置参数`default="默认参数"`即可设置默认值

![image-20221125114018006][]

### 使用Query进行校验 ###

@app02.get("/stu02/query/validate")
    def stu02_query_QueryValidate(
            param:str = Query(default= None,min_length=2,max_length=10,regex="^M")
    ):
        return {
        "param":param}

> 设置对应的参数即可进行校验，如上面的代码就是校验其最小长度为2，最大为10，而且利用正则表达式限定必须为`M`开头

![image-20221125114300454][]

![image-20221125114319627][]

*  更多参数可以直接看源码：

def Query(  # noqa: N802
        default: Any = Undefined,
        *,
        alias: Optional[str] = None, # 元数据 别名
        title: Optional[str] = None, # 元数据 标题
        description: Optional[str] = None, # 元数据 描述
        gt: Optional[float] = None, # 数值校验
        ge: Optional[float] = None,
        lt: Optional[float] = None,
        le: Optional[float] = None,
        min_length: Optional[int] = None,
        max_length: Optional[int] = None,
        regex: Optional[str] = None,
        example: Any = Undefined,
        examples: Optional[Dict[str, Any]] = None,
        deprecated: Optional[bool] = None,
        include_in_schema: bool = True,
        **extra: Any,
    )

### 传递列表 ###

@app02.get("/stu02/query/querylist")
    def stu02_query_QueryList(
            param_list: List[str] = Query(default=["List_01", "List_02", "List_03"], alias="参数别名")
    ):
        return {
        "param_list":param_list}

> 该示例即请求会传递一个列表的参数，FastAPI接收并返回。

![image-20221125115033359][]

### 声明必需参数 ###

在大多数情况下，需要某些东西时，可以简单地省略 `default` 参数，因此你通常不必使用 `...` 或 `Required`

@app02.get("/stu02/query/querymust")
    def stu02_query_QueryMust(
            param:str,
            param_None: Optional[str] = Query(default=...), # 使其可以接受None
            param_Pydantic:str = Query(default=Required)
    ):
        return {
        "param":param,"param_None":param_None,"param_Pydantic":param_Pydantic}

> 上面三个参数都是必需的参数；
> 
> param参数没有默认值，就被解析为必需参数；
> 
> param\_None参数利用Optional声明为可选的参数，再使用Query的…声明为必需参数；
> 
> param\_Pydantic参数利用Query的default参数设置为Required声明为必需的参数；
> 
> Required一个Pydantic内的任意类型的内置常量，源码：`Required: Any = Ellipsis`

![image-20221125115643456][]

### 源码 ###

# -*- coding: utf-8 -*-
    # @Time: 2022/11/24 21:40
    # @Author: MinChess
    # @File: stu02.py
    # @Software: PyCharm
    
    from fastapi import APIRouter,Query
    from typing import Optional,List
    
    from pydantic import Required
    
    app02 = APIRouter()
    
    # 查询参数
    @app02.get("/stu02/query")
    def stu02_query(query: float = 0.01):
        return {
        "query":query}
    
    # 可选参数
    @app02.get("/stu02/query/select")
    def stu02_query_select(string: Optional[float] = None,number:int = 1,optionalfloat:float = 6.33):
        return {
        "String":string,"Number":number,"optionalfloat":optionalfloat}
    
    # 类型转换
    @app02.get("/stu02/query/bool")
    def stu02_type_conversion(
            query:bool = False
    ):
        return {
        "布尔值":query}
    
    # 使用Query默认值
    @app02.get("/stu02/query/default")
    def stu02_query_QueryDefault(param:str = Query(default="QueryDefault")):
        return {
        "DefaultQuery":param}
    
    # 使用Query进行校验
    @app02.get("/stu02/query/validate")
    def stu02_query_QueryValidate(
            param:str = Query(default= None,min_length=2,max_length=10,regex="^M")
    ):
        return {
        "param":param}
    
    # 传递列表
    @app02.get("/stu02/query/querylist")
    def stu02_query_QueryList(
            param_list: List[str] = Query(default=["List_01", "List_02", "List_03"], alias="参数别名")
    ):
        return {
        "param_list":param_list}
    
    # 声明必需参数
    @app02.get("/stu02/query/querymust")
    def stu02_query_QueryMust(
            param:str,
            param_None: Optional[str] = Query(default=...), # 使其可以接受None
            param_Pydantic:str = Query(default=Required)
    ):
        return {
        "param":param,"param_None":param_None,"param_Pydantic":param_Pydantic}
    # 在大多数情况下，需要某些东西时，可以简单地省略 default 参数，因此你通常不必使用 ... 或 Required
    # Required: Any = Ellipsis 就是一个任意类型的内置常量

--------------------

感谢阅读  
博客链接：[https://blog.jiumoz.com/archives/fastapi-cong-ru-men-dao-shi-zhan-5-cha-xun-can-shu-yu-zi-fu-chuan-xiao-yan][https_blog.jiumoz.com_archives_fastapi-cong-ru-men-dao-shi-zhan-5-cha-xun-can-shu-yu-zi-fu-chuan-xiao-yan]

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[https_blog.jiumoz.com_archives_fastapi-cong-ru-men-dao-shi-zhan-5-cha-xun-can-shu-yu-zi-fu-chuan-xiao-yan]: https://blog.jiumoz.com/archives/fastapi-cong-ru-men-dao-shi-zhan-5-cha-xun-can-shu-yu-zi-fu-chuan-xiao-yan
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