Quadratic Formula in Python

qf.py

#!/usr/bin/env python
import math
import sys

def quad(a, b, c):
  disc = b**2 - 4*a*c
  if disc < 0:
    return None, None
  disc_sqrt = math.sqrt(disc)
  res_p = ((-b + disc_sqrt) / (2*a))
  res_n = ((-b - disc_sqrt) / (2*a))
  return res_p, res_n

if __name__ == "__main__":
  if len(sys.argv) < 4:
    sys.exit("usage: %s <a> <b> <c>" % sys.argv[0])
  res_p, res_n = quad(float(sys.argv[1]), float(sys.argv[2]), float(sys.argv[3]))
  if res_p is None:
    print("no solution")
  else:
    print("%.3f, %.3f" % (res_p, res_n))