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Response class

You can declare a parameter in a path operation function or dependency to be of type Response and then you can set data for the response like headers or cookies.

You can also use it directly to create an instance of it and return it from your path operations.

You can import it directly from fastapi:

from fastapi import Response

fastapi.Response 

Response(
    content=None,
    status_code=200,
    headers=None,
    media_type=None,
    background=None,
)
Source code in starlette/responses.py 
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def __init__(
    self,
    content: typing.Any = None,
    status_code: int = 200,
    headers: typing.Mapping[str, str] | None = None,
    media_type: str | None = None,
    background: BackgroundTask | None = None,
) -> None:
    self.status_code = status_code
    if media_type is not None:
        self.media_type = media_type
    self.background = background
    self.body = self.render(content)
    self.init_headers(headers)

media_type class-attribute instance-attribute 

media_type = None

charset class-attribute instance-attribute 

charset = 'utf-8'

status_code instance-attribute 

status_code = status_code

background instance-attribute 

background = background

body instance-attribute 

body = render(content)

headers property 

headers

render 

render(content)
Source code in starlette/responses.py 
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def render(self, content: typing.Any) -> bytes | memoryview:
    if content is None:
        return b""
    if isinstance(content, (bytes, memoryview)):
        return content
    return content.encode(self.charset)  # type: ignore

init_headers 

init_headers(headers=None)
Source code in starlette/responses.py 
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def init_headers(self, headers: typing.Mapping[str, str] | None = None) -> None:
    if headers is None:
        raw_headers: list[tuple[bytes, bytes]] = []
        populate_content_length = True
        populate_content_type = True
    else:
        raw_headers = [(k.lower().encode("latin-1"), v.encode("latin-1")) for k, v in headers.items()]
        keys = [h[0] for h in raw_headers]
        populate_content_length = b"content-length" not in keys
        populate_content_type = b"content-type" not in keys

    body = getattr(self, "body", None)
    if (
        body is not None
        and populate_content_length
        and not (self.status_code < 200 or self.status_code in (204, 304))
    ):
        content_length = str(len(body))
        raw_headers.append((b"content-length", content_length.encode("latin-1")))

    content_type = self.media_type
    if content_type is not None and populate_content_type:
        if content_type.startswith("text/") and "charset=" not in content_type.lower():
            content_type += "; charset=" + self.charset
        raw_headers.append((b"content-type", content_type.encode("latin-1")))

    self.raw_headers = raw_headers

set_cookie(
    key,
    value="",
    max_age=None,
    expires=None,
    path="/",
    domain=None,
    secure=False,
    httponly=False,
    samesite="lax",
)
Source code in starlette/responses.py 
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def set_cookie(
    self,
    key: str,
    value: str = "",
    max_age: int | None = None,
    expires: datetime | str | int | None = None,
    path: str | None = "/",
    domain: str | None = None,
    secure: bool = False,
    httponly: bool = False,
    samesite: typing.Literal["lax", "strict", "none"] | None = "lax",
) -> None:
    cookie: http.cookies.BaseCookie[str] = http.cookies.SimpleCookie()
    cookie[key] = value
    if max_age is not None:
        cookie[key]["max-age"] = max_age
    if expires is not None:
        if isinstance(expires, datetime):
            cookie[key]["expires"] = format_datetime(expires, usegmt=True)
        else:
            cookie[key]["expires"] = expires
    if path is not None:
        cookie[key]["path"] = path
    if domain is not None:
        cookie[key]["domain"] = domain
    if secure:
        cookie[key]["secure"] = True
    if httponly:
        cookie[key]["httponly"] = True
    if samesite is not None:
        assert samesite.lower() in [
            "strict",
            "lax",
            "none",
        ], "samesite must be either 'strict', 'lax' or 'none'"
        cookie[key]["samesite"] = samesite
    cookie_val = cookie.output(header="").strip()
    self.raw_headers.append((b"set-cookie", cookie_val.encode("latin-1")))

delete_cookie(
    key,
    path="/",
    domain=None,
    secure=False,
    httponly=False,
    samesite="lax",
)
Source code in starlette/responses.py 
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def delete_cookie(
    self,
    key: str,
    path: str = "/",
    domain: str | None = None,
    secure: bool = False,
    httponly: bool = False,
    samesite: typing.Literal["lax", "strict", "none"] | None = "lax",
) -> None:
    self.set_cookie(
        key,
        max_age=0,
        expires=0,
        path=path,
        domain=domain,
        secure=secure,
        httponly=httponly,
        samesite=samesite,
    )