import re
cases = ["test_TEST bfd",
"test_TEST_TEST_1_TEST_13DAHA bfd",
"test_TEST_TEST_1_TEST__13DAHA bfd",
"test__TEST_TEST",
"test_TEST__DHJF",
"test_TEST__Ddsa"
]
pattern = re.compile(r'_([0-9A-Z]+(?:_[0-9A-Z]+)*)(?:__[0-9A-Z_]+)?')
for case in cases:
match = pattern.search(case)
if match:
print(match.group(1))
aW1wb3J0IHJlCmNhc2VzID0gWyJ0ZXN0X1RFU1QgYmZkIiwKICAgICJ0ZXN0X1RFU1RfVEVTVF8xX1RFU1RfMTNEQUhBIGJmZCIsCiAgICAidGVzdF9URVNUX1RFU1RfMV9URVNUX18xM0RBSEEgYmZkIiwKICAgICJ0ZXN0X19URVNUX1RFU1QiLAogICAgInRlc3RfVEVTVF9fREhKRiIsCiAgICAidGVzdF9URVNUX19EZHNhIgpdCnBhdHRlcm4gPSByZS5jb21waWxlKHInXyhbMC05QS1aXSsoPzpfWzAtOUEtWl0rKSopKD86X19bMC05QS1aX10rKT8nKQpmb3IgY2FzZSBpbiBjYXNlczoKCW1hdGNoID0gcGF0dGVybi5zZWFyY2goY2FzZSkKCWlmIG1hdGNoOgoJCXByaW50KG1hdGNoLmdyb3VwKDEpKQ==