input: def compress(s):
      """Compress a given string by replacing all repeating characters with a single instance and its count.
      >>> compress("aabbbbbbcccc")
      '2a6b4c'
      """
      # Initialize results
      output = ""
  
      # Initialize count
      count = 1
  
      # Traverse the string
      for i in range(len(s)):
  
          # If the current character is same
          # as next one, increment its count
          if (i + 1 < len(s) and s[i] == s[i + 1]):
              count += 1
  
          else:
              # Append the count and character
              output += str(count) + s[i]
  
              # Reset the count
              count = 1
  
      return output
output:     # Initialize results
      output = ""
  
      # Initialize count
      count = 1
  
      # Traverse the string
      for i in range(len(s)):
  
          # If the current character is same
          # as next one, increment its count
          if (i + 1 < len(s) and s[i] == s[i + 1]):
              count += 1
  
          else:
              # Append the count and character
              output += str(count) + s[i]
  
              # Reset the count
              count = 1
  
      return output