str_l = ["aaa。bbb。", "aaa。", "aaa", "。"]
for str1 in str_l:
lst = str1.split(r"。")
nr = len(lst)
print(f"'{str1}' -> {nr == 1 or nr == 2 and lst[1] == ''}")
c3RyX2wgPSBbImFhYeOAgmJiYuOAgiIsICJhYWHjgIIiLCAiYWFhIiwgIuOAgiJdCgpmb3Igc3RyMSBpbiBzdHJfbDoKICAgIGxzdCA9IHN0cjEuc3BsaXQociLjgIIiKQogICAgbnIgPSBsZW4obHN0KQogICAgcHJpbnQoZiIne3N0cjF9JyAtPiB7bnIgPT0gMSBvciBuciA9PSAyIGFuZCBsc3RbMV0gPT0gJyd9Iik=