import os
s = "20200702_abcd_ef_aed_usd_cdee_hgd.csv"
print( os.path.splitext(s)[0].split('_', 1)[-1] )
import re
print( re.sub(r'^\d+_|\.[^.]*$', '', s) )
aW1wb3J0IG9zCnMgPSAiMjAyMDA3MDJfYWJjZF9lZl9hZWRfdXNkX2NkZWVfaGdkLmNzdiIKcHJpbnQoIG9zLnBhdGguc3BsaXRleHQocylbMF0uc3BsaXQoJ18nLCAxKVstMV0gKQoKaW1wb3J0IHJlCnByaW50KCByZS5zdWIocideXGQrX3xcLlteLl0qJCcsICcnLCBzKSAp