Problems with _csv.Error: sequence expected

Question

I have a list of python dictionaries that I'm trying to write the values into csv file, but for some reason I keep getting _csv.Error: sequence expected

Here is the sample code:

import csv
import os, sys

headers = ['id', 'Info']
data = [{'id': 1, 'Info': 'Example 1'}, {'id': 2, 'Info':'Example 2'}]

with open('all_csv.csv', 'wt') as f:
   writer = csv.writer(f, delimiter=',')
   writer.writerow(headers)
   for each in data:
      writer.writerow(each.values())

Any help would be appreciated.

Jean-François Fabre · Accepted Answer · 2018-09-06 15:12:00Z

1

in python 3, values() doesn't return a list anymore. You have to convert it first:

writer.writerow(list(each.values()))

note that dictionaries aren't ordered, so the order of the columns isn't defined (unless you're using Python 3.6 or higher), so maybe you want to use a csv.DictWriter object instead to avoid that your header doesn't match your rows.

Here's how I'd do it using csv.DictWriter:

import csv

data = [{'id': 1, 'Info': 'Example 1'}, {'id': 2, 'Info':'Example 2'}]

with open('all_csv.csv', 'w', newline="") as f:
   writer = csv.DictWriter(f, fieldnames = data[0], delimiter=',')
   writer.writeheader()
   writer.writerows(data)

the output is:

Info,id
Example 1,1
Example 2,2

answered Sep 6, 2018 at 15:12

Jean-François Fabre♦

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3 Comments

Helen Neely Over a year ago

Thanks for your amazing help. The header is in 9 columns, is there a way of simply defining the headers in a list? I noticed that my output has now jumbled up :(

Jean-François Fabre Over a year ago

passing headers as fieldnames should be ok too. But the fieldnames must match the keys exactly.

Helen Neely Over a year ago

You are a life saver :)

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