Create CSV output with an uneven dictionary of single values and lists

Question

I am using python and running my example on google colab. I am new to csv writing. I want to csv write out like the following. desired output example The issue I am having is with my lists in 'add' and 'reg'. When I run my example code I get the following. my output What should I do to get my desired output? Below is my attempt. If there is another post that has a similar situation as mine could you link it as I have already tried searching and could not find someone with the the issue as mine.

d = [{'local_date': '12/16/2022', 'local_time': '12:00', 'add':[2, 8, 22, 17], 'reg':[1001, 1002, 1003, 1004] }]
fields = ['local_date', 'local_time', 'add', 'reg']

with open("tester.csv", "w") as outfile:
  writer = csv.DictWriter(outfile, fieldnames = fields)
  writer.writeheader()
  writer.writerows(d)

`writerows` expects a list of rows; since `d` has only one element, it only prints one row. — Scott Hunter, Jun 15 '22 at 19:20
is pandas an option?, otherwise you will need to create a loop to get the values for the last 2 rows — Hanna, Jun 15 '22 at 19:31

Rodrigo · Answer 1 · 2022-06-15T19:42:17.900

One of the problems is that you're combining lists with other types of objects.

You could just put the other objects as lists, also if keys are in the dictionary, variable 'fields' becomes unnecessary.

Here is my try:

d = {'local_date': ['12/16/2022','12/16/2022','12/16/2022','12/16/2022'], 'local_time': ['12:00','12:00','12:00','12:00'], 'add':[2, 8, 22, 17], 'reg':[1001, 1002, 1003, 1004] }

with open("tester.csv", "w") as outfile:
  writer = csv.writer(outfile)
  writer.writerow(d.keys())
  writer.writerows(zip(*d.values()))

Also, if you don't have a limit on libraries, try pandas (it will make your life easier).

More info about lists in CSV: Write dictionary of lists to a CSV file

score 0 · Accepted Answer · answered Jun 15 '22 at 20:18

using csv

import csv

d = [{'local_date': '12/16/2022', 'local_time': '12:00', 'add':[2, 8, 22, 17], 'reg':[1001, 1002, 1003, 1004]}]

fields = ['local_date', 'local_time', 'add', 'reg']

# we parse the d list to get the create new row with each add, reg value
data = [{**dat, 'add':add, 'reg':reg} for dat in d for add, reg in zip(dat['add'], dat['reg'])]

with open("tester.csv", "w") as outfile:
  writer = csv.DictWriter(outfile, fieldnames = fields)
  writer.writeheader()
  writer.writerows(data)

using pandas

import pandas as pd

d = [{'local_date': '12/16/2022', 'local_time': '12:00', 'add':[2, 8, 22, 17], 'reg':[1001, 1002, 1003, 1004]}]

df = pd.DataFrame(d).explode(['add', 'reg'])

df.to_csv('tester.csv', index=False)

.explode() is new to me. I will look more into it. I appreciate your time. Thank you! — Joe, Jun 15 '22 at 20:21
@user19347158 you're welcome, here the documentation https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.explode.html — Hanna, Jun 15 '22 at 20:23

Create CSV output with an uneven dictionary of single values and lists

2 Answers2

using csv

using pandas