Question

I have a very long loop, and I would like to check the status every N iterations, in my specific case I have a loop of 10 million elements and I want to print a short report every millionth iteration.

So, currently I am doing just (n is the iteration counter):

if (n % 1000000==0):
    print('Progress report...')

but I am worried I am slowing down the process by computing the modulus at each iteration, as one iteration lasts just few milliseconds.

Is there a better way to do this? Or shouldn’t I worry at all about the modulus operation?

Answer 1

How about keeping a counter and resetting it to zero when you reach the wanted number? Adding and checking equality is faster than modulo.

printcounter = 0

# Whatever a while loop is in Python
while (...):   
    ...
    if (printcounter == 1000000):
        print('Progress report...')
        printcounter = 0
    ...
    printcounter += 1

Although it’s quite possible that the compiler is doing some sort of optimization like this for you already… but this may give you some peace of mind.