yoba = [(None, None), (None, 'Smack my Bitch Up'), ('The Prodigy', None), ('The Prodigy', 'Smack my Bitch Up')]
def dologic(A, B):
if None in (A, B):
return A or B or "..."
else:
return str.format("{} - {}", A, B)
for A, B in yoba:
print(dologic(A, B))
eW9iYSA9IFsoTm9uZSwgTm9uZSksIChOb25lLCAnU21hY2sgbXkgQml0Y2ggVXAnKSwgKCdUaGUgUHJvZGlneScsIE5vbmUpLCAoJ1RoZSBQcm9kaWd5JywgJ1NtYWNrIG15IEJpdGNoIFVwJyldCgpkZWYgZG9sb2dpYyhBLCBCKToKICAgIAogICAgaWYgTm9uZSBpbiAoQSwgQik6CiAgICAJCiAgICAJcmV0dXJuIEEgb3IgQiBvciAiLi4uIgogICAgCQogICAgZWxzZToKICAgIAkKICAgIAlyZXR1cm4gc3RyLmZvcm1hdCgie30gLSB7fSIsIEEsIEIpCiAgICAgICAgCmZvciBBLCBCIGluIHlvYmE6CiAgICBwcmludChkb2xvZ2ljKEEsIEIpKQ==