Convert between Windows style paths and POSIX style paths

[Noah]

Does anyone have a function to convert back and forth between
NT style paths and POSIX style? It seems trivial, but 
I want to make sure I don't overlook some obscure detail. 
Is it a simple matter of translating / and \ characters?

FYI, I need a Python function that does what cygpath does so that
I can run a script on either NT or UNIX or Cygwin.
I want my config files use one style of path.

Yours,
Noah