Python dictreader KeyError issue

Question

I am getting a keyerror when trying to read data from a csv. Below is the code that writes to the csv, followed by the code that reads from it. Python 2.7 on Ubuntu. Any help is appreciated!

    #setting up the csv
with open(databaseLocal, 'wb') as csvfile:
        fieldnames = ['cpu', 'pid', 'memory']
        writer = csv.DictWriter(csvfile, fieldnames=fieldnames, 
            quotechar='|', quoting=csv.QUOTE_MINIMAL)
        writer.writeheader()

#Here is one spot where it's written to...
if data[:6] == 'active':
                print 'mem info received'
                memInfo = data[7:-1]

                writer.writerow({'cpu': '_', 'pid': pidValue, 'memory': memInfo})

#and here is where it's read from, there is a KeyError for the line
#where we try to get row['pid]
with open(d, 'rb') as csvfile:
        reader = csv.DictReader(csvfile, delimiter=' ', quotechar='|')
        for row in reader:
            print row['pid']
            print row.keys()

When I just print 'row.keys()' all three of the keys show up. Not sure why I can't access 'row['pid'] or any of the others.

Thanks! Matt

Ignotas · Accepted Answer · 2015-01-14 04:42:22Z

1

You are writing to databaseLocal, but trying to read from d. Are you sure they are referencing the same file?

answered Jan 14, 2015 at 4:42

Ignotas

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6 Comments

Matt M Over a year ago

Sorry, maybe I should have included the previous line, which is 'for d in dbList:' and that databaseLocal should be included in dbList. If I comment out the print row['pid'] and just leave print row.keys(), I can clearly see that the rows are there.

Matt M Over a year ago

If I just say print row instead of print row['key'], it prints out this '{'cpu,pid,memory': '_,13330,1336811520'} '

Ignotas Over a year ago

It looks like the reader incorrectly parses the file. Try setting the fieldnames parameter when creating the DictReader: reader = csv.DictReader(csvfile, fieldnames=fieldnames, quotechar='|')

Matt M Over a year ago

OK here's an interesting development! It does work to say 'print row['cpu,pid,memory']'. It then prints out all three values. Did I somehow make it all one big key?

Ignotas Over a year ago

Yes, looks like you did. As I said, the DictReader incorrectly parses the input, so you need to specify the fieldnames.

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