sending a dataframe using flask route to be saved as csv

Question

I'm doing a Get request that includes the data from the dataframe, which I convert to csv.

'/dash/urlToDownload?value={}'.format(df.to_csv(index=False, 
sep=',',                                                                      
encoding='utf-8'))

The route looks as follows;

@app.server.route('/dash/urlToDownload')
def download_csv():
    value = flask.request.args.get('value')
    # create a dynamic csv or file here using `StringIO`
    # (instead of writing to the file system)
    strIO = io.StringIO()
    strIO.write(value)

    writer = csv.writer(strIO, delimiter=',', quotechar='|')
    writer.writerow(value)

    mem = io.BytesIO()
    mem.write(strIO.getvalue().encode('utf-8'))

    mem.seek(0)
    strIO.close()
    return flask.send_file(mem,
                     mimetype='text/csv',
                     attachment_filename='downloadFile.csv',
                     as_attachment=True)

I do get a csv file, but it doesn't recognize new lines and everything is written in the first row.

An example of what the variable value looks like;

version,id,value1,2,3

it seems that there are no characters between value and 1 to indicate a new line.

Why do you send that data via a GET request?Try POST? Have you tried logging the data you have 1) after receiving 2) before returning? — Florian H, Jun 28 '19 at 09:35
I'm working in Dash, and this it the way they recommend to download data to a file. It seems that value is missing a line-break character. The last value of row1 is connected to the first of row2. — John Dign, Jun 28 '19 at 09:44
Did you try adding `newline=''` argument in the `csv.writer()` constructor? — Prahlad Yeri, Jun 28 '19 at 10:50
It is since python 3 and required for [proper handling of carriage return (CRLF) on windows](https://stackoverflow.com/a/3191811/849365). Are you running python 3 or 2.x? — Prahlad Yeri, Jun 28 '19 at 11:18
You can also use lineterminator='\n' if newline doesn't work. — Prahlad Yeri, Jun 28 '19 at 11:19
Im using python 3, also check update explanation of the example :) — John Dign, Jun 28 '19 at 11:28

sending a dataframe using flask route to be saved as csv

0 Answers0