python 3 multithreading output to CSV file (blank) - multithreading

Question

I am new to python, i have got this multithreading working from a tutorial i ran across.
Unsure if it is goo practice or not.
What i want to archive:
pings the list of hostnames and returns up or down.
writes results to csv file
What this file currently does is:
pings the list of hostnames and returns up or down.
the csv file it creates is empty and doesnt appear to write any results to it.
I have done some testing and found that with the pings multithreadin over serial code is approx 16 times faster for me.
I am doing massive amounts of pings approx 9000 and want them returned asap.
Can you please let me know where i have gone wrong with the csv part.
import threading
from queue import Queue
import time
import subprocess as sp
import csv
# lock to serialize console output
lock = threading.Lock()
def do_work(item):
#time.sleep(1) # pretend to do some lengthy work.
# Make sure the whole print completes or threads can mix up output in one line.
status,result = sp.getstatusoutput("ping -n 3 " + str(item))
if status == 0:
result = 'Up'
else:
result = 'Down'
with lock:
output.writerow({'hostname': item,'status': result})
array.append({'hostname': item,'status': result})
print(threading.current_thread().name,item,result)
# The worker thread pulls an item from the queue and processes it
def worker():
while True:
item = q.get()
do_work(item)
q.task_done()
# Create the queue and thread pool.
q = Queue()
for i in range(100):
t = threading.Thread(target=worker)
t.daemon = True # thread dies when main thread (only non-daemon thread) exits.
t.start()
array = []
# stuff work items on the queue (in this case, just a number).
start = time.perf_counter()
headers = ['status','hostname']
output = csv.DictWriter(open('host-export.csv','w'), delimiter=',', lineterminator='\n', fieldnames=headers)
output.writeheader()
txt = open("hosts.txt", 'r', encoding="utf8")
for line in txt:
q.put(line,array)
q.join() # block until all tasks are done
# "Work" took .1 seconds per task.
# 20 tasks serially would be 2 seconds.
# With 4 threads should be about .5 seconds (contrived because non-CPU intensive "work")
print(array)
print('time:',time.perf_counter() - start)
I also added bulk writing for the csv thinking maybe i just cant access the csv object in the function but that also didnt work as below.
headers = ['status','hostname']
output = csv.DictWriter(open('host-export.csv','w'), delimiter=',', lineterminator='\n', fieldnames=headers)
output.writeheader()
output.writerows(array)

Answer 1

I fiugured out what i have done wrong.
I didnt close the file connection so it didnt write to the file.
here is the code i am using now to site my csv file.
fieldnames = ['ip', 'dns', 'pings'] #headings
test_file = open('test2-p.csv','w', newline='') #open file
csvwriter = csv.DictWriter(test_file, delimiter=',', fieldnames=fieldnames) #set csv writing settings
csvwriter.writeheader() #write csv headings
for row in rows: #write to csv file
csvwriter.writerow(row)
test_file.close()