You need to use a raw string first, 'r' or 'R' as follows:
In [01]: s = r'greenland.gdb\topology_check\t_buildings'
Then split while remembering to escape the backslash
In [02]: s.split('\\')
Out [02]: ['greenland.gdb', 'topology_check', 't_buildings']
Quoting from re — Regular expression operations (Python documentation)
\ Either escapes special characters (permitting you to match
characters like '*', '?', and so forth), or signals a special
sequence; special sequences are discussed below.
If you’re not using a raw string to express the pattern, remember that
Python also uses the backslash as an escape sequence in string
literals; if the escape sequence isn’t recognized by Python’s parser,
the backslash and subsequent character are included in the resulting
string. However, if Python would recognize the resulting sequence, the
backslash should be repeated twice. This is complicated and hard to
understand, so it’s highly recommended that you use raw strings for
all but the simplest expressions.