Python ValueError I/O operation on closed file

Question

I know this sounds a common error which has been asked multiple times on stackoverflow. However, I am pretty sure my issue is new as I read through almost the related topics.

I have two files as follows:

ALL_USER_PATH = 'all.csv'
NEW_USER_PATH = 'new.csv'

I open the "all" file for reading first

with open(ALL_USER_PATH, "r") as f:
    df = pd.read_csv(f) #pd is pandas
    f.close()

Next, I delete the content of the "new" file and get ready to write new data to it

if os.path.isfile(NEW_USER_PATH):
    os.remove(NEW_USER_PATH)

Write to it and it works fine

with open(NEW_USER_PATH, "a") as csv_n:
    #writer_n is to write new users
    writer_n = csv.writer(csv_n, delimiter=",", lineterminator='\n')
    for user in customer_records:         
        if checkExistence(df): # a method I wrote before
            continue
        else:    
            writer_n.writerow([data_to_be_written])

Next, I delete the "all" file and write new data to it

if os.path.isfile(ALL_USER_PATH):
    os.remove(ALL_USER_PATH)

with open(ALL_USER_PATH, "a") as csv_a:
    writer_a = csv.writer(csv_n, delimiter=",", lineterminator='\n')

    for user in customer_records:
        writer_a.writerow([all_data_to_be_written])

The error

"ValueError i/o operation on closed file"

is thrown herein at the last line to write data to the "all" file. I think it is because I opened it before, but I do remember to close it after reading the data, don't I? Could somebody please let me know what the problem is?

Solution

I also had that error but found another question with an answer and it worked.

After you leave the indented block under with open (csv file.csv) as csv: it will close the file.

with open('ALL_USER_PATH','a') as csv_a:
    writer_a = csv.writer(csv_n, delimiter=",", lineterminator='\n')
    # Here the file stays open
# Here the file is closed

I hope I managed to help.