请求文件¶

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English version

你可以使用 File 定义由客户端上传的文件。

信息

要接收上传的文件，请先安装 python-multipart。

请确保你创建一个虚拟环境、激活它，然后安装，例如：

$ pip install python-multipart

这是因为上传文件是以「表单数据」发送的。

导入 `File`¶

从 fastapi 导入 File 和 UploadFile：

Python 3.9+

from typing import Annotated

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: Annotated[bytes, File()]):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile):
    return {"filename": file.filename}

🤓 Other versions and variants

Python 3.10+Python 3.10+ - non-AnnotatedPython 3.9+ - non-Annotated

from typing import Annotated

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: Annotated[bytes, File()]):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile):
    return {"filename": file.filename}

Tip

Prefer to use the Annotated version if possible.

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: bytes = File()):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile):
    return {"filename": file.filename}

Tip

Prefer to use the Annotated version if possible.

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: bytes = File()):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile):
    return {"filename": file.filename}

定义 `File` 参数¶

像为 Body 或 Form 一样创建文件参数：

Python 3.9+

from typing import Annotated

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: Annotated[bytes, File()]):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile):
    return {"filename": file.filename}

🤓 Other versions and variants

Python 3.10+Python 3.10+ - non-AnnotatedPython 3.9+ - non-Annotated

from typing import Annotated

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: Annotated[bytes, File()]):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile):
    return {"filename": file.filename}

Tip

Prefer to use the Annotated version if possible.

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: bytes = File()):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile):
    return {"filename": file.filename}

Tip

Prefer to use the Annotated version if possible.

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: bytes = File()):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile):
    return {"filename": file.filename}

信息

File 是直接继承自 Form 的类。

但要注意，从 fastapi 导入的 Query、Path、File 等项，实际上是返回特定类的函数。

提示

声明文件体必须使用 File，否则，这些参数会被当作查询参数或请求体（JSON）参数。

文件将作为「表单数据」上传。

如果把路径操作函数参数的类型声明为 bytes，FastAPI 会为你读取文件，并以 bytes 的形式接收其内容。

请注意，这意味着整个内容会存储在内存中，适用于小型文件。

不过，在很多情况下，使用 UploadFile 会更有优势。

含 `UploadFile` 的文件参数¶

将文件参数的类型声明为 UploadFile：

Python 3.9+

from typing import Annotated

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: Annotated[bytes, File()]):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile):
    return {"filename": file.filename}

🤓 Other versions and variants

Python 3.10+Python 3.10+ - non-AnnotatedPython 3.9+ - non-Annotated

from typing import Annotated

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: Annotated[bytes, File()]):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile):
    return {"filename": file.filename}

Tip

Prefer to use the Annotated version if possible.

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: bytes = File()):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile):
    return {"filename": file.filename}

Tip

Prefer to use the Annotated version if possible.

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: bytes = File()):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile):
    return {"filename": file.filename}

与 bytes 相比，使用 UploadFile 有多项优势：

无需在参数的默认值中使用 File()。
它使用“spooled”文件：
- 文件会先存储在内存中，直到达到最大上限，超过该上限后会写入磁盘。
因此，非常适合处理图像、视频、大型二进制等大文件，而不会占用所有内存。
你可以获取上传文件的元数据。
它提供 file-like 的 async 接口。
它暴露了一个实际的 Python SpooledTemporaryFile 对象，你可以直接传给期望「file-like」对象的其他库。

`UploadFile`¶

UploadFile 的属性如下：

filename：上传的原始文件名字符串（str），例如 myimage.jpg。
content_type：内容类型（MIME 类型 / 媒体类型）的字符串（str），例如 image/jpeg。
file：SpooledTemporaryFile（一个 file-like 对象）。这是实际的 Python 文件对象，你可以直接传递给其他期望「file-like」对象的函数或库。

UploadFile 具有以下 async 方法。它们都会在底层调用对应的文件方法（使用内部的 SpooledTemporaryFile）。

write(data)：将 data（str 或 bytes）写入文件。
read(size)：读取文件中 size（int）个字节/字符。
seek(offset)：移动到文件中字节位置 offset（int）。
- 例如，await myfile.seek(0) 会移动到文件开头。
- 如果你先运行过 await myfile.read()，然后需要再次读取内容时，这尤其有用。
close()：关闭文件。

由于这些方法都是 async 方法，你需要对它们使用 await。

例如，在 async 路径操作函数 内，你可以这样获取内容：

contents = await myfile.read()

如果是在普通 def 路径操作函数 内，你可以直接访问 UploadFile.file，例如：

contents = myfile.file.read()

注意

当你使用这些 async 方法时，FastAPI 会在线程池中运行相应的文件方法并等待其完成。

注意

FastAPI 的 UploadFile 直接继承自 Starlette 的 UploadFile，但添加了一些必要的部分，使其与 Pydantic 以及 FastAPI 的其他部分兼容。

什么是「表单数据」¶

HTML 表单（<form></form>）向服务器发送数据的方式通常会对数据使用一种「特殊」的编码，这与 JSON 不同。

FastAPI 会确保从正确的位置读取这些数据，而不是从 JSON 中读取。

注意

当不包含文件时，来自表单的数据通常使用「媒体类型」application/x-www-form-urlencoded 编码。

但当表单包含文件时，会编码为 multipart/form-data。如果你使用 File，FastAPI 会知道需要从请求体的正确位置获取文件。

如果你想进一步了解这些编码和表单字段，请参阅 MDN web docs for POST。

警告

你可以在一个路径操作中声明多个 File 和 Form 参数，但不能同时声明希望以 JSON 接收的 Body 字段，因为此时请求体会使用 multipart/form-data 编码，而不是 application/json。

这不是 FastAPI 的限制，而是 HTTP 协议的一部分。

可选文件上传¶

您可以通过使用标准类型注解并将 None 作为默认值的方式将一个文件参数设为可选:

Python 3.10+

from typing import Annotated

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: Annotated[bytes | None, File()] = None):
    if not file:
        return {"message": "No file sent"}
    else:
        return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile | None = None):
    if not file:
        return {"message": "No upload file sent"}
    else:
        return {"filename": file.filename}

🤓 Other versions and variants

Python 3.10+ - non-Annotated

Tip

Prefer to use the Annotated version if possible.

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: bytes | None = File(default=None)):
    if not file:
        return {"message": "No file sent"}
    else:
        return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile | None = None):
    if not file:
        return {"message": "No upload file sent"}
    else:
        return {"filename": file.filename}

带有额外元数据的 `UploadFile`¶

您也可以将 File() 与 UploadFile 一起使用，例如，设置额外的元数据:

Python 3.9+

from typing import Annotated

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: Annotated[bytes, File(description="A file read as bytes")]):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(
    file: Annotated[UploadFile, File(description="A file read as UploadFile")],
):
    return {"filename": file.filename}

🤓 Other versions and variants

Python 3.10+Python 3.10+ - non-AnnotatedPython 3.9+ - non-Annotated

from typing import Annotated

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: Annotated[bytes, File(description="A file read as bytes")]):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(
    file: Annotated[UploadFile, File(description="A file read as UploadFile")],
):
    return {"filename": file.filename}

Tip

Prefer to use the Annotated version if possible.

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: bytes = File(description="A file read as bytes")):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(
    file: UploadFile = File(description="A file read as UploadFile"),
):
    return {"filename": file.filename}

Tip

Prefer to use the Annotated version if possible.

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: bytes = File(description="A file read as bytes")):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(
    file: UploadFile = File(description="A file read as UploadFile"),
):
    return {"filename": file.filename}

多文件上传¶

FastAPI 支持同时上传多个文件。

它们会被关联到同一个通过「表单数据」发送的「表单字段」。

要实现这一点，声明一个由 bytes 或 UploadFile 组成的列表（List）：

Python 3.9+

from typing import Annotated

from fastapi import FastAPI, File, UploadFile
from fastapi.responses import HTMLResponse

app = FastAPI()


@app.post("/files/")
async def create_files(files: Annotated[list[bytes], File()]):
    return {"file_sizes": [len(file) for file in files]}


@app.post("/uploadfiles/")
async def create_upload_files(files: list[UploadFile]):
    return {"filenames": [file.filename for file in files]}


@app.get("/")
async def main():
    content = """
<body>
<form action="/files/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
<form action="/uploadfiles/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
</body>
    """
    return HTMLResponse(content=content)

🤓 Other versions and variants

Python 3.10+Python 3.10+ - non-AnnotatedPython 3.9+ - non-Annotated

from typing import Annotated

from fastapi import FastAPI, File, UploadFile
from fastapi.responses import HTMLResponse

app = FastAPI()


@app.post("/files/")
async def create_files(files: Annotated[list[bytes], File()]):
    return {"file_sizes": [len(file) for file in files]}


@app.post("/uploadfiles/")
async def create_upload_files(files: list[UploadFile]):
    return {"filenames": [file.filename for file in files]}


@app.get("/")
async def main():
    content = """
<body>
<form action="/files/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
<form action="/uploadfiles/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
</body>
    """
    return HTMLResponse(content=content)

Tip

Prefer to use the Annotated version if possible.

from fastapi import FastAPI, File, UploadFile
from fastapi.responses import HTMLResponse

app = FastAPI()


@app.post("/files/")
async def create_files(files: list[bytes] = File()):
    return {"file_sizes": [len(file) for file in files]}


@app.post("/uploadfiles/")
async def create_upload_files(files: list[UploadFile]):
    return {"filenames": [file.filename for file in files]}


@app.get("/")
async def main():
    content = """
<body>
<form action="/files/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
<form action="/uploadfiles/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
</body>
    """
    return HTMLResponse(content=content)

Tip

Prefer to use the Annotated version if possible.

from fastapi import FastAPI, File, UploadFile
from fastapi.responses import HTMLResponse

app = FastAPI()


@app.post("/files/")
async def create_files(files: list[bytes] = File()):
    return {"file_sizes": [len(file) for file in files]}


@app.post("/uploadfiles/")
async def create_upload_files(files: list[UploadFile]):
    return {"filenames": [file.filename for file in files]}


@app.get("/")
async def main():
    content = """
<body>
<form action="/files/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
<form action="/uploadfiles/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
</body>
    """
    return HTMLResponse(content=content)

接收的也是含 bytes 或 UploadFile 的列表（list）。

注意

也可以使用 from starlette.responses import HTMLResponse。

fastapi.responses 其实与 starlette.responses 相同，只是为了方便开发者调用。实际上，大多数 FastAPI 的响应都直接从 Starlette 调用。

带有额外元数据的多文件上传¶

和之前的方式一样，你可以为 File() 设置额外参数，即使是 UploadFile：

Python 3.9+

from typing import Annotated

from fastapi import FastAPI, File, UploadFile
from fastapi.responses import HTMLResponse

app = FastAPI()


@app.post("/files/")
async def create_files(
    files: Annotated[list[bytes], File(description="Multiple files as bytes")],
):
    return {"file_sizes": [len(file) for file in files]}


@app.post("/uploadfiles/")
async def create_upload_files(
    files: Annotated[
        list[UploadFile], File(description="Multiple files as UploadFile")
    ],
):
    return {"filenames": [file.filename for file in files]}


@app.get("/")
async def main():
    content = """
<body>
<form action="/files/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
<form action="/uploadfiles/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
</body>
    """
    return HTMLResponse(content=content)

🤓 Other versions and variants

Python 3.10+Python 3.10+ - non-AnnotatedPython 3.9+ - non-Annotated

from typing import Annotated

from fastapi import FastAPI, File, UploadFile
from fastapi.responses import HTMLResponse

app = FastAPI()


@app.post("/files/")
async def create_files(
    files: Annotated[list[bytes], File(description="Multiple files as bytes")],
):
    return {"file_sizes": [len(file) for file in files]}


@app.post("/uploadfiles/")
async def create_upload_files(
    files: Annotated[
        list[UploadFile], File(description="Multiple files as UploadFile")
    ],
):
    return {"filenames": [file.filename for file in files]}


@app.get("/")
async def main():
    content = """
<body>
<form action="/files/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
<form action="/uploadfiles/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
</body>
    """
    return HTMLResponse(content=content)

Tip

Prefer to use the Annotated version if possible.

from fastapi import FastAPI, File, UploadFile
from fastapi.responses import HTMLResponse

app = FastAPI()


@app.post("/files/")
async def create_files(
    files: list[bytes] = File(description="Multiple files as bytes"),
):
    return {"file_sizes": [len(file) for file in files]}


@app.post("/uploadfiles/")
async def create_upload_files(
    files: list[UploadFile] = File(description="Multiple files as UploadFile"),
):
    return {"filenames": [file.filename for file in files]}


@app.get("/")
async def main():
    content = """
<body>
<form action="/files/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
<form action="/uploadfiles/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
</body>
    """
    return HTMLResponse(content=content)

Tip

Prefer to use the Annotated version if possible.

from fastapi import FastAPI, File, UploadFile
from fastapi.responses import HTMLResponse

app = FastAPI()


@app.post("/files/")
async def create_files(
    files: list[bytes] = File(description="Multiple files as bytes"),
):
    return {"file_sizes": [len(file) for file in files]}


@app.post("/uploadfiles/")
async def create_upload_files(
    files: list[UploadFile] = File(description="Multiple files as UploadFile"),
):
    return {"filenames": [file.filename for file in files]}


@app.get("/")
async def main():
    content = """
<body>
<form action="/files/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
<form action="/uploadfiles/" enctype="multipart/form-data" method="post">
<input name="files" type="file" multiple>
<input type="submit">
</form>
</body>
    """
    return HTMLResponse(content=content)

小结¶

使用 File、bytes 和 UploadFile 来声明在请求中上传的文件，它们以表单数据发送。

请求文件¶

导入 File¶

定义 File 参数¶

含 UploadFile 的文件参数¶

UploadFile¶

什么是「表单数据」¶

可选文件上传¶

带有额外元数据的 UploadFile¶

多文件上传¶

带有额外元数据的多文件上传¶

小结¶

导入 `File`¶

定义 `File` 参数¶

含 `UploadFile` 的文件参数¶

`UploadFile`¶

带有额外元数据的 `UploadFile`¶