Not able to parse a .csv file uploaded using Flask

Question

I am trying to upload a CSV file, work on it to produce results, and write back (download) a new CSV file containing the result. I am very new to Flask and I am not able to

Answer 1

Important note: This answer is relevant only for platforms where SpooledTemporaryFile is available.

Further to iLuveTux answer, you can save the redundant read() call by replacing the following string-based stream creation:

stream = io.StringIO(f.stream.read().decode("UTF8"), newline=None)

with:

stream = io.TextIOWrapper(f.stream._file, "UTF8", newline=None)

Example:

stream = io.TextIOWrapper(f.stream._file, "UTF8", newline=None)
csv_input = csv.reader(stream)
print(csv_input)
for row in csv_input:
    print(row)

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Further information:

Werkzeug default stream for form data parser is SpooledTemporaryFile (as of 1.0.1), from which you can obtain the underlying buffer using its _file memeber.