Exiting Python While True loop - python-3.x

Question

I am using a temperature sensor (HS18B20) on my raspberry pi. Every second or so, temperature is recorded onto a spreadsheet and sent to dropbox using a while True loop. It will do this forever until ctrl + c is pressed. In order to upload to dropbox, I cannot have the same file name as another file. The program will give an error and stop. Obviously, I could simply create a file with a different name everytime but to combat having hundreds of different files on dropbox, I delete the file on dropbox and immediately upload the new spreadsheet to dropbox. I have no problem with this technique, except for one thing...
If the program is stopped via ctrl + c right after the file is deleted and during the uploading of the file, the new file doesn't get uploaded and only gets deleted on dropbox (the local .xls file is never deleted; just replaced).
toc = time.strftime("%b %-d, %Y. %H:%M:%S")
dbx.files_delete('/Temperature Data ' + toc + '.xls')
with open(time.strftime("%m_%d_%Y") + '.xls', "rb") as f:
dbx.files_upload(f.read(), '/Temperature Data ' + toc + '.xls')
print("Uploaded to Dropbox")
I thought I set up a fail safe, but it still does not work.
Here is a snippet from my code.
def signal_handler(signal, frame):
signal interrupted
interrupted = True
signal.signal(signal.SIGINT, signal_handler)
interrupted = False
...
while True:
print("Temperature Taken")
a += 1
c += 1
if temp_f < input_bad:
ws.write(a,0,temp_f)
ws.write(a,1,time.strftime("%H:%M:%S %p"))
ws.write(a,2,"YES")
while c % 6 == 0:
c += 1
dbx.files_delete('/Temperature Data ' + toc + '.xls')
with open(time.strftime("%m_%d_%Y") + '.xls', "rb") as f:
dbx.files_upload(f.read(), '/Temperature Data ' + toc + '.xls')
print("Uploaded to Dropbox")
if interrupted:
print("Saving...")
dbx.files_delete('/Temperature Data ' + toc + '.xls')
with open(time.strftime("%m_%d_%Y") + '.xls',"rb") as f:
dbx.files_upload(f.read(), '/Temperature Data ' + toc + '.xls')
quit()
If I ctrl + c the program while it's taking a temperature readings, no problem! The program finishes its loop until c % 6 == 0 and then saves and closes.
If I ctrl + c the program while its saving, yes problem...
I could just print("Do not close the program") when its saving, but I would like to make this idiot proof.
Any tips? Thanks!

Answer 1

You can register a signal handler and the quit the loop when at the end of processing.
import signal
import sys
userQuitRequested = False
def signal_handler(signal, frame):
print('You pressed Ctrl+C!')
userQuitRequested = True
signal.signal(signal.SIGINT, signal_handler)
print('Press Ctrl+C to quit')
You can then check for userQuitRequested in your loop at the appropriate time, and break if True.