mirror of https://github.com/tiangolo/fastapi.git
49 lines
1.9 KiB
Markdown
49 lines
1.9 KiB
Markdown
You can define files to be uploaded by the client using `File`.
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## Import `File`
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Import `File` from `fastapi`:
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```Python hl_lines="1"
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{!./tutorial/src/request-files/tutorial001.py!}
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```
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## Define `File` parameters
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Create file parameters the same way you would for `Body` or `Form`:
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```Python hl_lines="7"
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{!./tutorial/src/request-files/tutorial001.py!}
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```
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The files will be uploaded as form data and you will receive the contents as `bytes`.
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!!! info
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`File` is a class that inherits directly from `Form`.
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!!! info
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To declare File bodies, you need to use `File`, because otherwise the parameters would be interpreted as query parameteres or body (JSON) parameters.
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## "Form Data"?
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The way HTML forms (`<form></form>`) sends the data to the server normally uses a "special" encoding for that data, it's different from JSON.
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**FastAPI** will make sure to read that data from the right place instead of JSON.
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!!! note "Technical Details"
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Data from forms is normally encoded using the "media type" `application/x-www-form-urlencoded` when it doesn't include files.
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But when the form includes files, it is encoded as `multipart/form-data`. If you use `File`, **FastAPI** will know it has to get the files from the correct part of the body.
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If you want to read more about these encondings and form fields, head to the <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/POST" target="_blank"><abbr title="Mozilla Developer Network">MDN</abbr> web docs for <code>POST</code></a>.
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!!! warning
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You can declare multiple `File` and `Form` parameters in an endpoint, but you can't also declare `Body` fields that you expect to receive as JSON, as the request will have the body encoded using `multipart/form-data` instead of `application/json`.
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This is not a limitation of **FastAPI**, it's part of the HTTP protocol.
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## Recap
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Use `File` to declare files to be uploaded as input parameters (as form data).
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