I would like to use data from a file called simdata.txt to run a simulation that I wrote in Python. I would like to ensure that when the user executes my program from the command line that the data is only being fed through the sys.stdin stream.
That is, I would like my program to be ran like this:
python3 simulation.py < simdata.txt
as opposed to this (fed through sys.argv as opposed to sys.stdin):
python3 simulation.py simdata.txt
How can I ensure that the user will always execute the program the first way as opposed to the second way? Usually I enforce this rule using this:
if len(sys.argv) > 2:
print("This is not how you use the program. Example of use:")
print("python3 simulation.py < simdata.txt")
exit(1)
But this seems problematic since I may want to add extra flags to my program that would change the behavior of the simulation. That is, maybe I would want to do this:
python3 simulation.py < simdata.txt --plot_data
Is there a better way to ensure that the simdata.txt is only fed through stdin without compromising my ability to add extra program flags?
Working with the argparse module turned out to be the better answer. That way I didn't have to have such strict requirements for input.