import re


def is_url(_str):
  """return true if the str input is a URL."""
  ur = re.findall('http[s]?://(?:[a-zA-Z]|[0-9]|[$-_@.&+]|[!*\(\), ]|(?:%[0-9a-fA-F][0-9a-fA-F]))+', _str)
  return len(ur) > 0