Not able to store data in a CSV file with a while loop

Question

I have problem to store data in a CSV file in Python. I am taking measurement from two different instruments and I want to store them in a CSV file. It is measuring continuously and I want to stop the measurement anytime with a key stroke.

My problem is that I only get a the header plus the first measurement and that's it. It is not looping and I don't understand why.

Here is the code:

data = []
stored_exception = None
file_name = ("Logger_")+str(time.strftime("%Y_%B_%d_%H_%M_%S"))+(".csv")
client = init_MKS(SERVER_HOST, SERVER_PORT)
scope = init_MSO()

# create a CSV file with header
write_CSV_file(file_name, 'w', HEADER)
print('------- Measurement started -------')
print('To stop the measurement press Ctrl+C\n')
try:    
    while True:
        valuesMKS = logger_MKS(client)
        valuesMSO = logger_MSO(scope)
        data.extend(valuesMSO)
        data.extend(valuesMKS)
        write_CSV_file(file_name, 'a', data)
        time.sleep(1) # Do not need all the data point
# Press Ctrl+C to stop the programm
except KeyboardInterrupt:
    print('------- Measurement stopped -------')
# Cheching errors of communications with MSO44
except visa.VisaIOError:
    print('ERROR!\nConnection lost')
    print('------- Measurement stopped -------\n')

logger_MKS uses a Modbus protocole and logger_MSO a LabVIEW visa protocol. Here is the function I created to create or store the data:

def write_CSV_file(file, mode_file, data):
    with open(file, mode=mode_file,  newline='') as backup_file:
        writer_file = csv.writer(backup_file, delimiter=';')
        writer_file.writerow(data)
        backup_file.close()

I know it is not the best way open and close continuously a CSV I am not a computer science engineer and it the safest way to be sure the data are stored somewhere is the computer shuts down (it happens sometimes)

Many thanks for your help