FlickrFan – find the Mac default pictures folder

sys.UnixShellCommand("osascript -e '(path to pictures folder) as string'")

More better (since you get a newline at the end of the above)
string.trimWhiteSpace(sys.unixShellCommand("osascript -e '(path to pictures folder) as string'"))

The list of possible “magic” folders in AppleScript

Get multiple folder paths in one swell foop

osascript -e '{(path to pictures folder) as string, (path to applications folder) as string}'

returns a comma-separated list.