Flask-Python import data from csv file

Question

I am trying to import a csv file from a webpage using flask. I am able to import the data from the csv file and return the data as json. However, I would like to print only the first sample from the data. I have attached my code and the flask error below. The csv file I am using is csvfile. The returned json data looks something like this

{
  "result": [
    [
      "0.011223", 
      "0.018274", 
      "0.071568", 
      "0.3407", 
      "0.50367", 
      "0.63498", 
      "0.45607", 
      "0.39945", 
      "0.27201", 
      "0.23569", 
      "0.29102", 
      "0.15327", 
      "0.095266", 
      "0.059091", 
      "0.014877", 
      "0.00010369", 
      "0.049384", 
      "0.12681", 
      "0.24325", 
      "0.30725", 
      "0.4259", 
      "0.56476", 
      "0.606", 
      "0.1001", 
      "0.5427", 
      "0.63342", 
      "0.62526", 
      "0.59211", 
      "0.59013", 
      "0.50669", 
      "0.42666", 
      "0.29487", 
      "0.20149",

Please advice what is wrong with the script.

`from flask import Flask, request, jsonify, render_template
 from flask.ext import excel
 import json, csv

 app=Flask(__name__)
 app.debug = True

 @app.route("/upload", methods=['GET', 'POST'])
 def upload_file():
   if request.method == 'POST':
       a= jsonify({"result": request.get_array(field_name='file')})
       entries  = json.loads(a)
       entry=entries['result'][0]
       return "<h2>'entry=%f'</h2>"%entry
   return '''
     <!doctype html>
     <title>Upload an excel file</title>
     <h1>Excel file upload (csv, tsv, csvz, tsvz only)</h1>
     <form action="" method=post enctype=multipart/form-data><p>
     <input type=file name=file><input type=submit value=Upload>
     </form>
      '''


  if __name__ == "__main__":
  app.run()`

TypeError
TypeError: expected string or buffer

Traceback (most recent call last)
File "C:\Users\Vikrant\Desktop\Flask1\chap1\lib\site-packages\flask\app.py", line 1836, in __call__
return self.wsgi_app(environ, start_response)
File "C:\Users\Vikrant\Desktop\Flask1\chap1\lib\site-packages\flask\app.py", line 1820, in wsgi_app
response = self.make_response(self.handle_exception(e))
File "C:\Users\Vikrant\Desktop\Flask1\chap1\lib\site-packages\flask\app.py", line 1403, in handle_exception
reraise(exc_type, exc_value, tb)
File "C:\Users\Vikrant\Desktop\Flask1\chap1\lib\site-packages\flask\app.py", line 1817, in wsgi_app
response = self.full_dispatch_request()
File "C:\Users\Vikrant\Desktop\Flask1\chap1\lib\site-packages\flask\app.py", line 1477, in full_dispatch_request
rv = self.handle_user_exception(e)
File "C:\Users\Vikrant\Desktop\Flask1\chap1\lib\site-packages\flask\app.py", line 1381, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "C:\Users\Vikrant\Desktop\Flask1\chap1\lib\site-packages\flask\app.py", line 1475, in full_dispatch_request
rv = self.dispatch_request()
File "C:\Users\Vikrant\Desktop\Flask1\chap1\lib\site-packages\flask\app.py", line 1461, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "C:\Users\Vikrant\Desktop\Flask1\Flaskr\flaskr_t2.py", line 12, in upload_file
entries  = json.loads(a)
File "c:\python27\Lib\json\__init__.py", line 339, in loads
return _default_decoder.decode(s)
File "c:\python27\Lib\json\decoder.py", line 364, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
TypeError: expected string or buffer
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score 0 · Answer 1 · edited May 23 '17 at 12:31

I guess the issue here is with jsonify.

According to the docs:

flask.json.jsonify(*args, **kwargs)

Creates a Response with the JSON representation of the given arguments with an application/json mimetype.

(See also this answer.)

You'd typically use it to send a json to a client (like in an API, for instance) and let it handle the protocol stuff.

When writing this:

   a= jsonify({"result": request.get_array(field_name='file')})
   entries  = json.loads(a)

it looks like you expect it to return just the json data, not a full response.

Did you try to print a and see what's in there? You may also want to print request.get_array(field_name='file') as it looks like you are serializing then deserializing the data.

Flask-Python import data from csv file

1 Answers1