I’m performing some calculations to generate chaotic solutions to a mathematical function. I have an infinite loop that looks something like this:
f = open('solutions.csv', 'a')
while True:
x = generate_random_parameters() # x is a list of floats
success = test_parameters(x)
if success:
print(','.join(map(str, x)), file=f, flush=True)
The implementation of generate_random_parameters() and test_parameters() is not very important here.
When I want to stop generating solutions I want to ^C, but I want to ensure that solutions.csv keeps its integrity/doesn’t get corrupted/etc, in case I happen to interrupt when the file is being written to.
So far I haven’t observed this happening, but I’d like to remove any possibility that this could occur.
Additionally, since the program will never terminate on its own I don’t have a corresponding f.close() — this should be fine, correct?
Appreciate any clarification.
2
One simple approach to ensuring that the current call to print finishes before the program exits from a keyboard interrupt is to use a signal handler to unset a flag on which the while loop runs.
Set the signal handler only when you’re about to call print and reset the signal handler to the original when print returns, so that the preceding code in the loop can be interrupted normally:
import signal
def interrupt_handler(signum, frame):
global running
running = False
text = 'a' * 99999
running = True
with open('solutions.csv', 'a') as f:
while running:
... # your calculations
original_handler = signal.signal(signal.SIGINT, interrupt_handler)
print(text, file=f, flush=True) # your output
signal.signal(signal.SIGINT, original_handler)
Also note that it is more idiomatic to use open as a context manager to handle the closure of an open file when exiting the block for any reason.
3
It’s generally good practice to use the with context manager anytime you’re opening a file, it will auto handle file closure and be generally safer to ctrl-c out of.(pylint,pep)
with open('solutions.csv', 'a') as f:
while True:
x = generate_random_parameters()
success = test_parameters(x)
if success:
print(','.join(map(str, x)), file=f, flush=True)
Your code, is technically fine without using the context manager but in the event of an exception having file.close() execute is never a bad thing.
1