Check for presence fo directory

[Maurice LING]

Hi, I'm looking for a way to check the presence of a directory, such as, 
  finddirectory(d), where d is the full directory path. Or is the only 
way  is to use os.listdir() to get the directory list and test for the 
presence of the directory I want before creating one?

What will happen if I try to create a directory that is already present?

Thanks
Maurice