import re
string = """TokenRange(start_token:5835456583056758754, end_token:5867789857766669245, rack:brikbrik0),EndpointDetails(host:192.168.210.183, datacenter:DC1, rack:brikbrikadfdas), EndpointDetails(host:192.168.210.182, datacenter:DC1, rack:brikbrik1adf)])"""
rx = re.compile(r'\brack:(\w+)')
matches = [match.group(1) for match in rx.finditer(string)]
print(matches)
aW1wb3J0IHJlCnN0cmluZyA9ICIiIlRva2VuUmFuZ2Uoc3RhcnRfdG9rZW46NTgzNTQ1NjU4MzA1Njc1ODc1NCwgZW5kX3Rva2VuOjU4Njc3ODk4NTc3NjY2NjkyNDUsIHJhY2s6YnJpa2JyaWswKSxFbmRwb2ludERldGFpbHMoaG9zdDoxOTIuMTY4LjIxMC4xODMsIGRhdGFjZW50ZXI6REMxLCByYWNrOmJyaWticmlrYWRmZGFzKSwgRW5kcG9pbnREZXRhaWxzKGhvc3Q6MTkyLjE2OC4yMTAuMTgyLCBkYXRhY2VudGVyOkRDMSwgcmFjazpicmlrYnJpazFhZGYpXSkiIiIKcnggPSByZS5jb21waWxlKHInXGJyYWNrOihcdyspJykKCm1hdGNoZXMgPSBbbWF0Y2guZ3JvdXAoMSkgZm9yIG1hdGNoIGluIHJ4LmZpbmRpdGVyKHN0cmluZyldCnByaW50KG1hdGNoZXMp