import re
regex = r"\S+(?= \(KM\))"
strings = ["261.30 (NM) / 300.76 (MI) / 483.93 (KM)", "952.27 (NM) / 1,096.09 (MI) / 1,763.61 (KM)"]
for s in strings:
matches = re.search(regex, s)
if matches:
print(float(matches.group().replace(',', '')))
aW1wb3J0IHJlCgpyZWdleCA9IHIiXFMrKD89IFwoS01cKSkiCnN0cmluZ3MgPSBbIjI2MS4zMCAoTk0pIC8gMzAwLjc2IChNSSkgLyA0ODMuOTMgKEtNKSIsICI5NTIuMjcgKE5NKSAvIDEsMDk2LjA5IChNSSkgLyAxLDc2My42MSAoS00pIl0KCmZvciBzIGluIHN0cmluZ3M6CiAgICBtYXRjaGVzID0gcmUuc2VhcmNoKHJlZ2V4LCBzKQogICAgaWYgbWF0Y2hlczoKICAgICAgICBwcmludChmbG9hdChtYXRjaGVzLmdyb3VwKCkucmVwbGFjZSgnLCcsICcnKSkp