remove_alpha/digit

def remove_alpha(seqch):
# @param seqch: String
# return string
  new_string = ""
  for s in seqch:
    if not s.isalpha():
      new_string = new_string + s
  return new_string

def remove_digit(seqch):
# @param seqch: String
# return string
  new_string = ""
  for s in seqch:
    if not s.isdigit():
      new_string = new_string + s
  return new_string