Header 参数¶
定义 Header 参数的方式与定义 Query、Path、Cookie 参数相同。
导入 Header¶
首先，导入 Header：
from typing import Annotated
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(user_agent: Annotated[str | None, Header()] = None):
return {"User-Agent": user_agent}
🤓 Other versions and variants
from typing import Annotated, Union
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(user_agent: Annotated[Union[str, None], Header()] = None):
return {"User-Agent": user_agent}
from typing import Union
from fastapi import FastAPI, Header
from typing_extensions import Annotated
app = FastAPI()
@app.get("/items/")
async def read_items(user_agent: Annotated[Union[str, None], Header()] = None):
return {"User-Agent": user_agent}
Tip
Prefer to use the Annotated version if possible.
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(user_agent: str | None = Header(default=None)):
return {"User-Agent": user_agent}
Tip
Prefer to use the Annotated version if possible.
from typing import Union
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(user_agent: Union[str, None] = Header(default=None)):
return {"User-Agent": user_agent}
声明 Header 参数¶
然后，使用和 Path、Query、Cookie 一样的结构定义 header 参数。
第一个值是默认值，还可以传递所有验证参数或注释参数：
from typing import Annotated
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(user_agent: Annotated[str | None, Header()] = None):
return {"User-Agent": user_agent}
🤓 Other versions and variants
from typing import Annotated, Union
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(user_agent: Annotated[Union[str, None], Header()] = None):
return {"User-Agent": user_agent}
from typing import Union
from fastapi import FastAPI, Header
from typing_extensions import Annotated
app = FastAPI()
@app.get("/items/")
async def read_items(user_agent: Annotated[Union[str, None], Header()] = None):
return {"User-Agent": user_agent}
Tip
Prefer to use the Annotated version if possible.
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(user_agent: str | None = Header(default=None)):
return {"User-Agent": user_agent}
Tip
Prefer to use the Annotated version if possible.
from typing import Union
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(user_agent: Union[str, None] = Header(default=None)):
return {"User-Agent": user_agent}
技术细节
Header 是 Path、Query、Cookie 的兄弟类，都继承自共用的 Param 类。
注意，从 fastapi 导入的 Query、Path、Header 等对象，实际上是返回特殊类的函数。
说明
必须使用 Header 声明 header 参数，否则该参数会被解释为查询参数。
自动转换¶
Header 比 Path、Query 和 Cookie 提供了更多功能。
大部分标准请求头用连字符分隔，即减号（-）。
但是 user-agent 这样的变量在 Python 中是无效的。
因此，默认情况下，Header 把参数名中的字符由下划线（_）改为连字符（-）来提取并存档请求头 。
同时，HTTP 的请求头不区分大小写，可以使用 Python 标准样式（即 snake_case）进行声明。
因此，可以像在 Python 代码中一样使用 user_agent ，无需把首字母大写为 User_Agent 等形式。
如需禁用下划线自动转换为连字符，可以把 Header 的 convert_underscores 参数设置为 False：
from typing import Annotated
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(
strange_header: Annotated[str | None, Header(convert_underscores=False)] = None,
):
return {"strange_header": strange_header}
🤓 Other versions and variants
from typing import Annotated, Union
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(
strange_header: Annotated[
Union[str, None], Header(convert_underscores=False)
] = None,
):
return {"strange_header": strange_header}
from typing import Union
from fastapi import FastAPI, Header
from typing_extensions import Annotated
app = FastAPI()
@app.get("/items/")
async def read_items(
strange_header: Annotated[
Union[str, None], Header(convert_underscores=False)
] = None,
):
return {"strange_header": strange_header}
Tip
Prefer to use the Annotated version if possible.
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(
strange_header: str | None = Header(default=None, convert_underscores=False),
):
return {"strange_header": strange_header}
Tip
Prefer to use the Annotated version if possible.
from typing import Union
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(
strange_header: Union[str, None] = Header(default=None, convert_underscores=False),
):
return {"strange_header": strange_header}
警告
注意，使用 convert_underscores = False 要慎重，有些 HTTP 代理和服务器不支持使用带有下划线的请求头。
重复的请求头¶
有时，可能需要接收重复的请求头。即同一个请求头有多个值。
类型声明中可以使用 list 定义多个请求头。
使用 Python list 可以接收重复请求头所有的值。
例如，声明 X-Token 多次出现的请求头，可以写成这样：
from typing import Annotated
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(x_token: Annotated[list[str] | None, Header()] = None):
return {"X-Token values": x_token}
🤓 Other versions and variants
from typing import Annotated, List, Union
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(x_token: Annotated[Union[List[str], None], Header()] = None):
return {"X-Token values": x_token}
from typing import List, Union
from fastapi import FastAPI, Header
from typing_extensions import Annotated
app = FastAPI()
@app.get("/items/")
async def read_items(x_token: Annotated[Union[List[str], None], Header()] = None):
return {"X-Token values": x_token}
Tip
Prefer to use the Annotated version if possible.
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(x_token: list[str] | None = Header(default=None)):
return {"X-Token values": x_token}
Tip
Prefer to use the Annotated version if possible.
from typing import Union
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(x_token: Union[list[str], None] = Header(default=None)):
return {"X-Token values": x_token}
Tip
Prefer to use the Annotated version if possible.
from typing import List, Union
from fastapi import FastAPI, Header
app = FastAPI()
@app.get("/items/")
async def read_items(x_token: Union[List[str], None] = Header(default=None)):
return {"X-Token values": x_token}
与路径操作通信时，以下面的方式发送两个 HTTP 请求头：
X-Token: foo
X-Token: bar
响应结果是：
{
"X-Token values": [
"bar",
"foo"
]
}
小结¶
使用 Header 声明请求头的方式与 Query、Path 、Cookie 相同。
不用担心变量中的下划线，FastAPI 可以自动转换。