How to avoid repeating header when Writing to CSV in loop?

Question

I want to save the values of different variables in a CSV file. But it prints another header every time. I don't want this, I am attaching my CSV file snapshot for your understanding. Output csv

file_orimg = open('Org_image.csv', 'a', newline='')
writer_orimg = csv.writer(file_orimg, delimiter='\t',lineterminator='\n',)
writer_orimg.writerow(["Image Name", "epsilon","MSE", "SSIM", "Prediction", "Probability"])

for i in images:
     writer_orimg.writerow([i, epsilon, mse, ssim, clean_pred, clean_prob, label_idx.item()])

Answer 1

Try not to use writerow to write your headers. You can look at DictWriter in the CSV python module, writing headers and writing rows will be done more efficiently!

list_of_headers = ['No.', 'Image Name', 'Epsilon']
dictionary_content = {'No.': 1, 'Image Name': 'image_123', 'Epsilon': 'what?'}
w = csv.DictWriter(my_csvfile, fieldnames= list_of_headers)
w.writeheader()
w.writerow(dictionay_content)

Hope this helps, let me know if there is any rectification to be made!

Edit: Answering 'where & when should writeheader be done'

I use the os python module to determine whether the file exists, if not I'm going to create one!

if os.path.isfile(filename):
    with open(filename, 'a', newline='') as my_file:
        w = csv.DictWriter(my_file, fieldnames= list_of_headers)
        w.writerow(dictionay_content)
else:
    with open(filename, 'w', newline='') as my_file:
        w = csv.DictWriter(my_file, fieldnames= list_of_headers)
        w.writeheader()
        w.writerow(dictionay_content)

!!! Take note of the 'a' which is to append whereas 'w' means to write. Hence appending with new rows of your data from where it left off/last occupied.