Sensor data log csv in python

Question

I am new to programming and want to write a code for an infrared sensor to log a timestamp in a .csv file whenever it detects motion. So far I have found code for the detection but now need to add code to specify for it to write an entry in a csv file. Credits for motion detection code: https://www.modmypi.com/blog/raspberry-pi-gpio-sensing-motion-detection

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)
PIR_PIN = 7
GPIO.setup(PIR_PIN, GPIO.IN)

def MOTION(PIR_PIN):
print ("Motion Detected")

print ("PIR Module Test (CTRL+C to exit)")

time.sleep(2)
print ("Ready")

try:
    GPIO.add_event_detect(PIR_PIN, GPIO.RISING, callback=MOTION)
    while 1:
        time.sleep(100)

except KeyboardInterrupt:
    print("Quit")
    GPIO.cleanup()

Next I am trying to add something along the following lines which will then write in two columns TIMESTAMP and "motion detected":

import csv
import strftime 

row = [strfttime("%a, %d %b %Y %H:%M:%S"), motion_detected]    
with open('datalog.csv', 'a') as f:
    w = csv.writer(f)
    w.writerow(row)

I have only found ways to write to CSV's from static files so they didn't seem to provide a straightforward answer to my question. So any help in joining these codes or correcting the second would be great!

Answer 1

import RPi.GPIO as GPIO
import time
import csv
import strftime

GPIO.setmode(GPIO.BCM)
PIR_PIN = 7
GPIO.setup(PIR_PIN, GPIO.IN)

def MOTION(PIR_PIN):
    print ("Motion Detected")

    print ("PIR Module Test (CTRL+C to exit)")

    row = [strfttime("%a, %d %b %Y %H:%M:%S"), 'motion_detected']    
    with open('datalog.csv', 'a') as f:
        w = csv.writer(f)
        w.writerow(row)

    time.sleep(2)
    print ("Ready")

try:
    GPIO.add_event_detect(PIR_PIN, GPIO.RISING, callback=MOTION)
    while 1:
        time.sleep(100)

except KeyboardInterrupt:
    print("Quit")
    GPIO.cleanup()

Note: For a string motion detected, you need to add quotaion marks around it(in Python both single and double ones are supported).