Little command that returns 01, 02, 03... upon repeated calls. Good for automatic sequential numbering of simulations etc.

num

#!/usr/bin/python3
try:
	with open('num.txt') as ff:
		num = int(ff.read())+1
except FileNotFoundError:
	num=1
numstr = '{:02d}'.format(num)
print(numstr)
	
with open('num.txt', 'w') as ff:
	ff.write(numstr)