请求文件

你可以使用 File 定义客户端要上传的文件。

Info

要接收上传的文件，请先安装 python-multipart。

请确保创建一个虚拟环境，激活它，然后安装，例如：

$ pip install python-multipart

这是因为上传的文件以“表单数据”形式发送。

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 3.8+Python 3.8+ - non-Annotated

from fastapi import FastAPI, File, UploadFile
from typing_extensions import Annotated

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}

定义 File 参数

创建文件参数的方式与 Body 或 Form 相同：

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 3.8+Python 3.8+ - non-Annotated

from fastapi import FastAPI, File, UploadFile
from typing_extensions import Annotated

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}

Info

File 是一个直接从 Form 继承的类。

但请记住，当你从 fastapi 导入 Query、Path、File 等时，这些实际上是返回特殊类的函数。

Tip

要声明文件体，你需要使用 File，否则参数将被解释为查询参数或体（JSON）参数。

文件将作为“表单数据”上传。

如果你将路径操作函数参数的类型声明为 bytes，FastAPI 将为你读取文件，你将收到内容为 bytes。

请记住，这意味着整个内容将存储在内存中。这对于小文件很有效。

但在某些情况下，使用 UploadFile 可能会更有好处。

使用 UploadFile 的文件参数

使用 UploadFile 类型定义文件参数：

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 3.8+Python 3.8+ - non-Annotated

from fastapi import FastAPI, File, UploadFile
from typing_extensions import Annotated

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}

与 bytes 相比，使用 UploadFile 有几个优点：

• 你不必在参数的默认值中使用 File()。
• 它使用“假脱机”文件：
  • 文件存储在内存中，直到达到最大大小限制，超过此限制后，它将存储在磁盘上。
• 这意味着它适用于大文件，如图像、视频、大型二进制文件等，而不会消耗所有内存。
• 你可以从上传的文件中获取元数据。
• 它具有一个 类文件 async 接口。
• 它暴露了一个实际的 Python SpooledTemporaryFile 对象，你可以直接传递给其他期望类文件对象的库。

UploadFile

UploadFile 具有以下属性：

• filename：一个 str，包含上传的原始文件名（例如 myimage.jpg）。
• content_type：一个 str，包含内容类型（MIME 类型 / 媒体类型）（例如 image/jpeg）。
• file：一个 SpooledTemporaryFile（一个 类文件 对象）。这是实际的 Python 文件对象，你可以直接传递给其他期望“类文件”对象的函数或库。

UploadFile 具有以下 async 方法。它们都调用相应的文件方法（使用内部的 SpooledTemporaryFile）。

• write(data)：将 data（str 或 bytes）写入文件。
• read(size)：读取文件的 size（int）字节/字符。
• seek(offset)：转到文件中的字节位置 offset（int）。
  • 例如，await myfile.seek(0) 将转到文件的开头。
  • 如果你运行一次 await myfile.read() 然后需要再次读取内容，这尤其有用。
• close()：关闭文件。

由于所有这些方法都是 async 方法，你需要“await”它们。

例如，在 async 路径操作函数中，你可以通过以下方式获取内容：

contents = await myfile.read()

如果你在普通的 def 路径操作函数中，你可以直接访问 UploadFile.file，例如：

contents = myfile.file.read()

async 技术细节

当你使用 async 方法时，FastAPI 在线程池中运行文件方法并等待它们。

Starlette 技术细节

FastAPI 的 UploadFile 直接继承自 Starlette 的 UploadFile，但添加了一些必要的部分以使其与 Pydantic 和 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使用数据的“特殊”编码，它与 JSON 不同。

FastAPI 将确保从正确的位置读取数据，而不是从 JSON。

技术细节

来自表单的数据在不包含文件时通常使用“媒体类型” application/x-www-form-urlencoded 进行编码。

但是当表单包含文件时，它被编码为 multipart/form-data。如果你使用 File，FastAPI 将知道它必须从正文的正确部分获取文件。

如果你想了解更多关于这些编码和表单字段的信息，请前往 MDN web docs for POST。

Warning

你可以在路径操作中声明多个 File 和 Form 参数，但你不能同时声明期望以 JSON 形式接收的 Body 字段，因为请求将使用 multipart/form-data 而不是 application/json 对正文进行编码。

这不是 FastAPI 的限制，它是 HTTP 协议的一部分。

可选文件上传

你可以通过使用标准类型注解并将默认值设置为 None 来使文件可选：

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 3.9+Python 3.8+Python 3.10+ - non-AnnotatedPython 3.8+ - non-Annotated

from typing import Annotated, Union

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: Annotated[Union[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: Union[UploadFile, None] = None):
    if not file:
        return {"message": "No upload file sent"}
    else:
        return {"filename": file.filename}

from typing import Union

from fastapi import FastAPI, File, UploadFile
from typing_extensions import Annotated

app = FastAPI()


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

Tip

Prefer to use the Annotated version if possible.

from typing import Union

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: Union[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: Union[UploadFile, None] = None):
    if not file:
        return {"message": "No upload file sent"}
    else:
        return {"filename": file.filename}

带有附加元数据的 UploadFile

你也可以将 File() 与 UploadFile 一起使用，例如，设置附加元数据：

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 3.8+Python 3.8+ - non-Annotated

from fastapi import FastAPI, File, UploadFile
from typing_extensions import Annotated

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}

多文件上传

可以同时上传多个文件。

它们将与使用“表单数据”发送的同一个“表单字段”相关联。

要使用它，声明一个 bytes 或 UploadFile 的列表：

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 3.8+Python 3.9+ - non-AnnotatedPython 3.8+ - non-Annotated

from typing import List

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

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 typing import List

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)

你将收到，如声明的那样，一个 bytes 或 UploadFile 的 list。

技术细节

你也可以使用 from starlette.responses import HTMLResponse。

FastAPI 提供与 fastapi.responses 相同的 starlette.responses，只是为了方便你，开发者。但大多数可用的响应直接来自 Starlette。

带有附加元数据的多文件上传

与之前相同的方式，你可以使用 File() 设置附加参数，即使是对于 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 3.8+Python 3.9+ - non-AnnotatedPython 3.8+ - non-Annotated

from typing import List

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

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 typing import List

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)

回顾

使用 File、bytes 和 UploadFile 声明要在请求中上传的文件，作为表单数据发送。