请求头参数¶
你可以像定义 Query、Path 和 Cookie 参数一样定义请求头参数。
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¶
然后使用与 Path、Query 和 Cookie 相同的结构来声明请求头参数。
你可以定义默认值以及所有额外的验证或注解参数：
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 和 Cookie 的“姊妹”类。它同样继承自相同的通用 Param 类。
但请记住，当你从 fastapi 导入 Query、Path、Header 等时，这些实际上是返回特殊类的函数。
Info
要声明请求头，你需要使用 Header，否则参数将被解释为查询参数。
自动转换¶
Header 在 Path、Query 和 Cookie 提供的功能基础上还有一些额外功能。
大多数标准请求头使用“连字符”（即“减号”，-）分隔。
但像 user-agent 这样的变量在 Python 中是无效的。
因此，默认情况下，Header 会将参数名称中的下划线（_）转换为连字符（-）来提取和记录请求头。
此外，HTTP 请求头不区分大小写，因此你可以使用标准的 Python 风格（也称为“snake_case”）来声明它们。
所以，你可以像在 Python 代码中通常那样使用 user_agent，而不需要像 User_Agent 那样首字母大写。
如果出于某些原因你需要禁用下划线到连字符的自动转换，请将 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}
Warning
在将 convert_underscores 设置为 False 之前，请注意某些 HTTP 代理和服务器不允许使用带下划线的请求头。
重复的请求头¶
可能会收到重复的请求头。这意味着，同一个请求头具有多个值。
你可以在类型声明中使用列表来定义这些情况。
你将收到重复请求头的所有值作为一个 Python list。
例如，要声明一个可以出现多次的 X-Token 请求头，你可以这样写：
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}
如果你向该路径操作发送两个 HTTP 请求头：
X-Token: foo
X-Token: bar
响应将如下所示：
{
"X-Token values": [
"bar",
"foo"
]
}
回顾¶
使用 Header 声明请求头，采用与 Query、Path 和 Cookie 相同的通用模式。
无需担心变量中的下划线，FastAPI 会负责转换它们。