Remove repeated adjacent characters from string

Given a string like:
“aabbdeeeef”
or
“bbbbbbb”

we want to output:

“abdef”
and
“b”
respectively.

here are a few ways to do it in Python:

As a function:

Example 1

def RemoveAdjacentLetters(str):
  a=""
  for s in str:
    a+=s if s not in a else ""
  return a

Example 2

def RemoveAdjacentLetters(str):
  a=""
  for s in str:
    a+=("", num)[num not in a]
  return a

Example 3

def RemoveAdjacentLetters(str):
  a=""
  for s in str:
    if num not in a:
      a+=num
  return a

Example 4 – regular expression

def RemoveAdjacentLetters(n):
  return re.sub('(.)\1+', '\1', n)