如何将键从嵌套字典输出到csv

Question

I am trying to write a nested dictionary to CSV. I have been able to do this successfully, but because dictionary are not ordered, I can't tell which column is which. How can I output the keys as column headers to so that I can tell which column is which?

import datetime
import csv

d = {
        u'Project 1': {'Start Date': datetime.datetime(2015, 5, 6, 0, 0), 'Finish Date': datetime.datetime(2015, 12, 23, 0, 0)},
        u'Project 2': {'Start Date': datetime.datetime(2015, 1, 23, 0, 0), 'Finish Date': datetime.datetime(2015, 12, 22, 0, 0)}
}

milestones = d.values()[0].keys()
for key, value in d.items():
    print [key] + [d[key][date] for date in milestones]

writer = csv.writer(open('C:\\test.csv', 'wb'))
for key, value in d.items():
    writer.writerow([key] + [d[key][date] for date in milestones])

Answer 1

Use csv.DictWriter (this is an example, modify it to suit your needs):

import csv

with open('test.csv', 'w') as csvfile:
    # put all keys you want to write here
    fieldnames = ['Project Name', 'Start Date', 'Finish Date']
    writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
    writer.writeheader()

    for project_name, project_dict in d.iteritems():
        # add project name
        row_dict = dict(
            [("Project Name", project_name)] + project_dict.items()
        )
        # write row
        writer.writerow(row_dict)