import re
regex = r"(?::[:;]|[^;\n])+"
str = "foo;bar:;baz::;one:two;::three::::;four;;five:::;six;:seven;::eight"
print(re.findall(regex, str))
aW1wb3J0IHJlCgpyZWdleCA9IHIiKD86Ols6O118W147XG5dKSsiCnN0ciA9ICJmb287YmFyOjtiYXo6OjtvbmU6dHdvOzo6dGhyZWU6Ojo6O2ZvdXI7O2ZpdmU6Ojo7c2l4OzpzZXZlbjs6OmVpZ2h0IgpwcmludChyZS5maW5kYWxsKHJlZ2V4LCBzdHIpKQ==