KeyError reading csv file and transferring to array

Question

I have an example csv file with name 'r2.csv':

Factory | Product_Number |   Date     | Avg_Noshow | Walk_Cost | Room_Rev
-------------------------------------------------------------------------
   A    |      1         | 01APR2017  |   5.6      |  125      |  275
-------------------------------------------------------------------------
   A    |      1         | 02APR2017  |   4.5      |  200      |  300
-------------------------------------------------------------------------
   A    |      1         | 03APR2017  |   6.6      |  150      |  250
-------------------------------------------------------------------------
   A    |      1         | 04APR2017  |   7.5      |  175      |  325
-------------------------------------------------------------------------

I have the following python code to read a csv file and transfer the columns to arrays:

# Read csv file
import csv
with open('r2.csv', 'r') as infile:

   reader = csv.DictReader(infile)
   data = {}
   for row in reader:
       for header, value in row.items():
          try:
                data[header].append(value)
          except KeyError:
                data[header] = [value]

 # Transfer the column from list to arrays for later computation.

mu = data['Avg_Noshow']
cs = data['Walk_Cost']
co = data['Room_Rev']

mu = map(float,mu)
cs = map(float,cs)
co = map(float,co)

It runs fine except for the last row and has the following error message:

File "<stdin>", line 1, in <module>
  KeyError: 'Room_Rev'

How could I avoid it?

At first glance, shouldn't it be comma separated values instead of pipes? — Garrett Kadillak
– Garrett Kadillak, Commented Apr 18, 2017 at 21:23
@GarrettKadillak do you mean the csv file? It is comma separated value file. — Chenxi
– Chenxi, Commented Apr 18, 2017 at 21:29

gold_cy · Accepted Answer · 2017-04-18 21:47:08Z

1

I worked off just the top two rows of your csv but this gives you the desired output:

with open('r2.csv', 'rb') as fin:
    reader = csv.DictReader(fin)
    data = {}
    for row in reader:
        for k, v in row.iteritems():
            if k in data:
                data[k] = [data[k],v]
            else:
                data[k] = v

And this returns:

{'Avg_Noshow': ['5.6', '4.5'],
 'Date': ['1-Apr-17', '2-Apr-17'],
 'Factory': ['A', 'A'],
 'Product_Number': ['1', '1'],
 'Room_Rev': ['275', '300'],
 'Walk_Cost': ['125', '200']}

answered Apr 18, 2017 at 21:47

gold_cy

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2 Comments

Chenxi Over a year ago

Thank you @Dmitry Polonskiy I tried the code but it returns same error message as I posted.

Chenxi Over a year ago

Thank you! Error from input data of my side

martineau · Accepted Answer · 2017-04-18 22:28:43Z

0

I am unable to reproduce the problem using this cleaned-up version of your code:

# Read csv file
import csv
with open('r2.csv', 'r') as infile:
    reader = csv.DictReader(infile)
    data = {}
    for row in reader:
        print('row: {}'.format(row))
        for header, value in row.items():
            try:
                data[header].append(value)
            except KeyError:
                data[header] = [value]

print('')
from pprint import pprint
pprint(data)

# Transfer the column from list to arrays for later computation.

mu = data['Avg_Noshow']
cs = data['Walk_Cost']
co = data['Room_Rev']

mu = map(float, mu)
cs = map(float, cs)
co = map(float, co)

This is the printed output it produced:

 row: {'Walk_Cost': '125', 'Factory': 'A', 'Avg_Noshow': '5.6', 'Product_Number': '1', 'Date': '01APR2017', 'Room_Rev': '275'}
 row: {'Walk_Cost': '200', 'Factory': 'A', 'Avg_Noshow': '4.5', 'Product_Number': '1', 'Date': '02APR2017', 'Room_Rev': '300'}
 row: {'Walk_Cost': '150', 'Factory': 'A', 'Avg_Noshow': '6.6', 'Product_Number': '1', 'Date': '03APR2017', 'Room_Rev': '250'}
 row: {'Walk_Cost': '175', 'Factory': 'A', 'Avg_Noshow': '7.5', 'Product_Number': '1', 'Date': '04APR2017', 'Room_Rev': '325'}

 {'Avg_Noshow': ['5.6', '4.5', '6.6', '7.5'],
  'Date': ['01APR2017', '02APR2017', '03APR2017', '04APR2017'],
  'Factory': ['A', 'A', 'A', 'A'],
  'Product_Number': ['1', '1', '1', '1'],
  'Room_Rev': ['275', '300', '250', '325'],
  'Walk_Cost': ['125', '200', '150', '175']}

And this the r2.csv test I created myself and used since you didn't provide one:

Factory,Product_Number,Date,Avg_Noshow,Walk_Cost,Room_Rev
A,1,01APR2017,5.6,125,275
A,1,02APR2017,4.5,200,300
A,1,03APR2017,6.6,150,250
A,1,04APR2017,7.5,175,325

answered Apr 18, 2017 at 22:28

martineau

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2 Comments

Chenxi Over a year ago

thank you @martineau With your check information, I found I input one more 'space' in the column name 'Room_rev'. And now done.

martineau Over a year ago

Chenxi: You're welcome. Although sometimes ridiculed, just printing things at certain critical points in your code is a very old—and underrated—debugging technique. It's also especially suited for Python since there's no prolonged code compiling and linking steps to go through first.

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