Write list of dictionary into CSV Python

Question

Suppose I have the list of dictionary dataset like this,

data_set = [
    {'Active rate': [0.98, 0.97, 0.96]},
    {'Operating Expense': [3.104, 3.102, 3.101]}
]

I need to iterate the list of dictionary and put the keys as column headers and its values as the rows and write it to the CSV file.

Active rate    Operating Expense
0.98           3.104
0.97           3.102
0.96           3.101

This is what I tried

data_set = [
    {'Active rate': [0.98, 0.931588, 0.941192]},
    {'Operating Expense': [3.104, 2.352, 2.304]}
]

import csv

with open('names.csv', 'w') as csvfile:
    fieldnames = ['Active rate', 'Operating Expense']
    writer = csv.DictWriter(csvfile, fieldnames=fieldnames)

    writer.writeheader()
    writer.writerow({'Active rate': 0.98, 'Operating Expense': 3.102})
    writer.writerow({'Active rate': 0.97, 'Operating Expense': 3.11})
    writer.writerow({'Active rate': 0.96, 'Operating Expense': 3.109})

For brevity, I have reduced the keys to 2 and list of values to 3.

How to approach this problem?

Thanks

Answer 1

d1 = {'Active rate': [0.98, 0.931588, 0.941192]}
d2 = {'Operating Expense': [3.104, 2.352, 2.304]}

with open('names.csv', 'w') as csvfile:
    fieldnames = zip(d1, d2)[0]
    writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
    writer.writeheader()

    for row in zip(d1['Active rate'], d2['Operating Expense']):
        writer.writerow(dict(zip(fieldnames, row)))

For performance, you might want to use itertools.izip over zip depending on the length of lists.

Answer 2

The following approach should work for the data structure you have given:

import csv

data_set = [
    {'Active rate': [0.98, 0.97, 0.96]},
    {'Operating Expense': [3.104, 3.102, 3.101]}
]

fieldnames = ['Active rate', 'Operating Expense']
rows = []

for field in fieldnames:
    for data in data_set:
        try:
            rows.append(data[field])
            break
        except KeyError, e:
            pass

with open('names.csv', 'wb') as f_output:
    csv_output = csv.writer(f_output)
    csv_output.writerow(fieldnames)
    csv_output.writerows(zip(*rows))

Giving you the following CSV output file:

Active rate,Operating Expense
0.98,3.104
0.97,3.102
0.96,3.101