从多个字典写入单个 CSV 文件

Question

Background

I have multiple dictionaries of different lengths. I need to write the values of dictionaries to a single CSV file. I figured I can loop through each dictionary one by one and write the data to CSV. I ran in to a small formatting issue.

Problem/Solution

I realized after I loop through the first dictionary the data of the second writing gets written the row where the first dictionary ended as displayed in the first image I would ideally want my data to print as show in the second image

My Code

import csv

    e = {'Jay':10,'Ray':40}
    c = {'Google':5000}

    def writeData():
        with open('employee_file20.csv', mode='w') as csv_file:
            fieldnames = ['emp_name','age','company_name','size']
            writer = csv.DictWriter(csv_file, fieldnames=fieldnames)
            writer.writeheader()

            for name in e:
                 writer.writerow({'emp_name':name,'age':e.get(name)})

            for company in c:
                writer.writerow({'company_name':company,'size':c.get(company)})


    writeData()

PS: I would have more than 2 dictionaries so I am looking for a generic way where I can print data from row under the header for all the dictionaries. I am open to all solutions and suggestions.

Answer 1

If all dictionaries are of equal size, you could use zip to iterate over them in parallel. If they aren't of equal size, and you want the iteration to pad to the longest dict, you could use itertools.zip_longest

For example:

import csv
from itertools import zip_longest

e = {'Jay':10,'Ray':40}
c = {'Google':5000}

def writeData():
    with open('employee_file20.csv', mode='w') as csv_file:
        fieldnames = ['emp_name','age','company_name','size']
        writer = csv.writer(csv_file)
        writer.writerow(fieldnames)

        for employee, company in zip_longest(e.items(), c.items()):
            row = list(employee)
            row += list(company) if company is not None else ['', '']  # Write empty fields if no company

            writer.writerow(row)

writeData()

If the dicts are of equal size, it's simpler:

import csv

e = {'Jay':10,'Ray':40}
c = {'Google':5000, 'Yahoo': 3000}

def writeData():
    with open('employee_file20.csv', mode='w') as csv_file:
        fieldnames = ['emp_name', 'age', 'company_name', 'size']
        writer = csv.writer(csv_file)
        writer.writerow(fieldnames)

        for employee, company in zip(e.items(), c.items()):
            writer.writerow(employee + company)

writeData()

A little side note: If you use Python3, dictionaries are ordered. This isn't the case in Python2. So if you use Python2, you should use collections.OrderedDict instead of the standard dictionary.

Answer 2

There might be a more pythonic solution, but I'd do something like this:

I haven't used your .csv writer thing before, so I just made my own comma separated output.

e = {'Jay':10,'Ray':40}
c = {'Google':5000}
dict_list = [e,c] # add more dicts here.
max_dict_size = max(len(d) for d in dict_list)
output = ""
# Add header information here.
for i in range(max_dict_size):
  for j in range(len(dict_list)):
    key, value = dict_list[j].popitem() if len(dict_list[j]) else ("","")
    output += f"{key},{value},"
  output += "\n"
# Now output should contain the full text of the .csv file
# Do file manipulation here.
# You could also do it after each row,
# Where I currently have the output += "\n"

Edit: A little more thinking and I found something that might polish this a bit. You could first map the dictionary into a list of keys using the .key() function on each dictionary and appending those to an empty list.

The advantage with that is that you'd be able to go "forward" instead of popping the dictionary items off the back. It also wouldn't destroy the dictionary.