old_contents: #!/usr/bin/env python
  
  import sys
  rcool=float(sys.argv[1])
  
  for l in open('cooling_time.dat'):
      r,t=l.split()
      r=float(r)
      t=float(t)
      if r>rcool:
          print("cooling time at %f kpc=%f Gyr"%(rcool,t))
          sys.exit(0)
  
new_contents: #!/usr/bin/env python3
  #
  # Extract the cooling time corresponding to the cooling radius.
  #
  # Junhua GU
  # 2012-12-20
  # Weitian LI
  # 2016-06-07
  #
  
  import argparse
  import numpy as np
  
  
  def get_tcool(data, rcool):
      """
      Get the cooling time *at* the specified cooling radius.
  
      XXX: whether to interpolate first?
      """
      radius = data[:, 0]
      ctime = data[:, 1]
      tcool = np.min(ctime[radius > rcool])
      return tcool
  
  
  def main():
      parser = argparse.ArgumentParser(
              description="Extract cooling time w.r.t the given cooling radius")
      parser.add_argument("infile", help="input cooling time data file")
      parser.add_argument("rcool", type=float, help="cooling radius (kpc)")
      args = parser.parse_args()
  
      data = np.loadtxt(args.infile)
      tcool = get_tcool(data, rcool=args.rcool)
      print("cooling time at %f kpc=%f Gyr" % (args.rcool, tcool))
      print("cooling_time= %f Gyr" % tcool)
      print("cooling_radius= %f kpc" % args.rcool)
  
  
  if __name__ == "__main__":
      main()
  
subject: Rewrite extract_tcool.py