Parse input natively with argparse instead of creating a separate function

[bobleesj]

Potential area of improvement

As discussed in #3 (comment), the tup function below is used to parse a string of two integers separated by a comma.

diffpy.nmf_mapping/diffpy/nmf_mapping/nmf_mapping/main.py

Lines 36 to 44 in 57eb972

	def tup(s):
	if not isinstance(s, str):
	raise TypeError("Input must be a string of two integers separated by a comma.")
	try:
	l, h = map(int, s.split(","))
	return l, h
	except ValueError:
	raise ValueError("Input must be two integers separated by a comma (e.g., '1,5')")

tup is used as an input to the parser.add_argument function shown below:

diffpy.nmf_mapping/diffpy/nmf_mapping/nmf_mapping/main.py

Lines 100 to 107 in 57eb972

	)
	parser.add_argument(
	"--xrange",
	default=None,
	type=tup,
	nargs="*",
	help="the x-range over which to calculate NMF, can be multiple ranges (e.g. --xrange 5,10 12,15)",
	)

Suggestion

Recommended by @sbillinge , instead of creating a separate nested function called tup, we shall use argparse to parse the input more gracefully. I am currently not so familiar with the argparse library at the moment. Once we are done with the cookiecutting release process, we can re-visit this problem.