double each char of a string python code example

Example: double char python

def doubleChar(str):
  lisp = list(str)
  out = []
  string = ''
  for i in range(len(lisp)):
    out.append(lisp[i])
    out.append(lisp[i])
  for i in range(len(out)):
    string += out[i]
  return string