Python Flask "send_file()" method TypeError

Question

I'm trying to read an image that the user uploads and then display the image back to them. I want to do this without saving the image file that is uploaded.

I have code like this:

from flask import Flask, redirect, render_template, request, url_for, send_file
from PIL import Image, ImageDraw
from io import BytesIO

app = Flask(__name__)


@app.route('/', methods=['GET', 'POST'])
def index():
    if request.method == 'POST':
        img = Image.open(request.files['file'].stream)
        byte_io = BytesIO()
        img.save(byte_io, 'PNG')
        byte_io.seek(0)
        return send_file(byte_io, mimetype='image/png')


if __name__ == '__main__':
    app.run(debug=1)

It produces this error:

TypeError: send_file() got an unexpected keyword argument 'mimetype'

I've tried replacing mimetype with other valid parameters and it will just give the same error but with the name of the new parameter. So I think the problem is with my bytes_io.

UPDATE:

To clarify, by send_file() I'm referring to the built in flask.send_file() method:

The code is flawless. Maybe you redefined send_file(). Attach full code. — Smart Manoj
– Smart Manoj, Commented Aug 21, 2022 at 3:16

davidism · Accepted Answer · 2022-07-04 01:34:36Z

6

From flask document

The mimetype guessing requires a filename or an attachment_filename to be provided.

...

mimetype – the mimetype of the file if provided. If a file path is given, auto detection happens as fallback, otherwise an error will be raised.

So, you should provide that like this

return send_file(
    io.BytesIO(obj.logo.read()),
    download_name='logo.png',
    mimetype='image/png'
)

This sample code should run normally,

from flask import Flask, request, send_file
app = Flask(__name__)

@app.route('/get_image')
def get_image():
    if request.args.get('type') == '1':
       filename = 'ok.gif'
    else:
       filename = 'error.gif'
    return send_file(filename)


if __name__ == '__main__':
    app.run()

If you've still got same error, maybe it's an environment problem. You can check your package version using pip freeze.

edited Jul 4, 2022 at 1:34

davidism

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answered Dec 5, 2017 at 5:52

hyun

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4 Comments

David Skarbrevik Over a year ago

Thanks, I tried adding attachment_filename and also as_attachment parameters but the error remains the same. I also tried your way of using BytesIO(file.read()) but that didn't change anything either :/

hyun Over a year ago

By the way, When I run your code in my mac, everything is ok...If you provide attachment_filename, how about remove mimetype? Because it will try to guess the mimetype by default, and plz check your flask version.

David Skarbrevik Over a year ago

I'm using the latest version of Flask (0.12.0 I think it was). I tried taking out send_file from my import statement and somehow the error is still the same, doesn't give any kind of send_file not defined type error... not sure what to make of that.

Smart Manoj Over a year ago

Doesn't answer the question.

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