Error with send_file using flask in Python

Question

I have an application where, through a server, the user needs to download a CSV file and an image that is stored in the same directory as the .py file but it doesn´t work. Here are my python code:

app = Flask(__name__)

@app.route('/', methods= ['POST', 'GET'])
def result():
    if request.method == 'GET':
        return render_template('result.html')
    elif request.method == 'POST':
             
            if request.form['submit_button'] == 'Download CSV':
                return send_file('name.csv', as_attachment=True, download_name='name.csv')
                

            elif request.form['submit_button'] == 'Download plot':
                return Flask.send_static_file('static/plot.png', as_attachment=True, download_name='plot.png')
                              
    

if __name__ == '__main__':
    app.run(debug = True, host='0.0.0.0')

Here are my html code:

<div class = 'wrap'>
     
 
    <form method="POST">

        <input type="submit" name="submit_button" value="Download CSV">
        <input type="submit" name="submit_button" value="Download plot">

    </form>
</div>

And here are my directories:

However, when I try to download it, I get the following error:

Thank you very much!!! I hope you can help me!

The error message tells you EXACTLY what you have done wrong. You need `return send_file(...)`. And by the way, you have misspelled "Download". — Tim Roberts, Jun 13 '23 at 21:54
Does this answer your question? [Flask send\_file not sending file](https://stackoverflow.com/questions/53747258/flask-send-file-not-sending-file) — gla3dr, Jun 13 '23 at 22:04
@gla3dr I add the return but it doesnt work and with the same error — Juan Ignacio Ochotorena, Jun 14 '23 at 08:19
@TimRoberts Thanks!! I correct the lines and add the return but the same error persists — Juan Ignacio Ochotorena, Jun 14 '23 at 08:20
Have you printed `request.form['submit_button']` to see what you get? If it doesn't match either string, you will return nothing. — Tim Roberts, Jun 14 '23 at 18:29

gla3dr · Answer 1 · 2023-06-13T22:29:30.983

0

The error message tells you exactly what is wrong.

The function either returned None or ended without a return statement.

You are not returning any response from the view function when the request is a POST. The send_file function returns a Response object, that you then need to return from the view function. So, you just need to do

                return send_file('name.csv', as_attachment=True, download_name='name.csv')

edited Jun 13 '23 at 22:29

answered Jun 13 '23 at 21:58

gla3dr

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I have applied the changes but it still doesn't work, I keep getting the same error – Juan Ignacio Ochotorena Jun 13 '23 at 22:19

Error with send_file using flask in Python

1 Answers1