How to write dictionary data to csv file?

Question

I have a dictionary like this. I want to write the data inside to csv file but I will run my code over and over again. How can I make it write headers only once? How can I remove the spaces between the lines?

My code

import csv

dl = {7: {'id': 11, 'name': 'Abc', 'age': 35},
      25: {'id': 28, 'name': 'refd', 'age': 88},
      15: {'id': 45, 'name': 'dfgd', 'age': 20}}
id_list = [7, 25, 15]

def to_csv(data):
    fieldnames = ['id', 'name', 'age']
    with open('data.csv', 'a+') as f:
        dict_writer = csv.DictWriter(f, fieldnames = fieldnames)
        dict_writer.writeheader()
        dict_writer.writerow(data)

for i in id_list:
    to_csv(dl[i])

for empty lines solution is

with open('data.csv', newline='', 'a+') as f:

first rub output:

first rub output

second run output:

second run output

jackal · Accepted Answer · 2022-03-26 17:23:38Z

2

How about passing a value to your function to indicate whether or not the headers should be written? Something like this:

def to_csv(data, writeheader):
    fieldnames = ['id', 'name', 'age']
    with open('data.csv', 'a+') as f:
        dict_writer = csv.DictWriter(f, fieldnames = fieldnames)
        if writeheader:
            dict_writer.writeheader()
        dict_writer.writerow(data)
id_list = [7,25,15]
for i in id_list:
    to_csv(dl[i], i==id_list[0])

edited Mar 26, 2022 at 17:23

answered Mar 26, 2022 at 16:59

jackal

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3 Comments

axbxcx Over a year ago

My fault. It isn't like 1-2-3 actually. Ids are like 5-9-50-2-715. I shared it this way as an example. I will fix it.

jackal Over a year ago

Edited to suit the changed question

axbxcx Over a year ago

Same logic. Right. :D I think this will work for me. Any idea about empty rows?

Ivan Kwong · Accepted Answer · 2022-03-26 16:49:20Z

0

dict_writer.writeheader()  # write the header in your file
dict_writer.writerow(data)  # write the data in your file

So instead of looping these two lines, you should only run writeheader once and run the writerow function multiple times.

I will let you figure out the actual implementation

answered Mar 26, 2022 at 16:49

Ivan Kwong

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2 Comments

axbxcx Over a year ago

But i run this code multiple times. How i can run writeheader once? I should check if my csv file has header if it has then dont run writeheader. But couldn't do it.

Ivan Kwong Over a year ago

Answer from @arthur.king would work, but I personally think this is not a good idea to run the to_csv function every time you loop the row. A better approach would be to process all your data in to_csv function.

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