new_contents: """Sometimes, we just want to zero out a precip event."""
  import datetime
  import glob
  import os
  import sys
  
  
  def do(fn, date):
      """Do."""
      with open(fn, encoding="utf-8") as fh:
          data = fh.read()
      dt2 = date + datetime.timedelta(days=1)
      pos1 = data.find(date.strftime("%-d\t%-m\t%Y"))
      pos2 = data.find(dt2.strftime("%-d\t%-m\t%Y"))
      if -1 in [pos1, pos2]:
          print("Couldn't find date in", fn)
          return
      myline = data[pos1:pos2].split("\n")[0]
      tokens = myline.split("\t")
      tokens[3] = "0"
  
      with open(f"new{fn}", "w", encoding="utf-8") as fh:
          fh.write(data[:pos1])
          fh.write("\t".join(tokens) + "\n")
          fh.write(data[pos2:])
  
      os.rename(f"new{fn}", fn)
  
  
  def main(argv):
      """Go main."""
      date = datetime.date(int(argv[1]), int(argv[2]), int(argv[3]))
      os.chdir("/i/0/cli")
      for zone in glob.glob("*"):
          os.chdir(zone)
          for fn in glob.glob("*.cli"):
              do(fn, date)
          os.chdir("..")
  
  
  if __name__ == "__main__":
      main(sys.argv)
  
subject: add tool for zeroing precip