Flask: Download a csv file on clicking a button

Question

I just got started with Flask/Python. What I want to achieve is that I have a download button in my HTML and it calls the following function:

function downloadPlotCSV() {
        $.ajax({
            url: "/getPlotCSV",
            type: "post",
            success: function(data) {
                dataPlot = JSON.parse(data);
                console.log(dataPlot);
            }
        });
    }

The incomplete flask code is:

@app.route('/getPlotCSV', methods = ['POST'])
def plotCSV():
    data = open("outputs/Adjacency.csv")

The problem I am facing is that I cannot find a way to download this csv file or return it as a JSON string so I can download it using Javascript. Any idea how I can send it as JSON or maybe download it via Flask itself? What’s the best way?

Asked By: Tarun Dugar

||

Source

Answer 1

Firstly you need to import from flask make_response, that will generate your response and create variable, something like response.
Secondly, make response.content_type = "text/csv"
Thirdly – return your response.

Answered By: wanderlust

Answer 2

Here is one way to download a CSV file with no Javascript:

#!/usr/bin/python

from flask import Flask, Response
app = Flask(__name__)

@app.route("/")
def hello():
    return '''
        <html><body>
        Hello. <a href="/getPlotCSV">Click me.</a>
        </body></html>
        '''

@app.route("/getPlotCSV")
def getPlotCSV():
    # with open("outputs/Adjacency.csv") as fp:
    #     csv = fp.read()
    csv = '1,2,3n4,5,6n'
    return Response(
        csv,
        mimetype="text/csv",
        headers={"Content-disposition":
                 "attachment; filename=myplot.csv"})


app.run(debug=True)

Answered By: Robᵩ

Answer 3

You can use flask.send_file() to send a static file:

from flask import send_file

@app.route('/getPlotCSV') # this is a job for GET, not POST
def plot_csv():
    return send_file(
        'outputs/Adjacency.csv',
        mimetype='text/csv',
        download_name='Adjacency.csv',
        as_attachment=True
    )

_{Prior to Flask 2.0, download_name was called attachment_filename.}

Answered By: kay

Flask: Download a csv file on clicking a button

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