How do I simplify this Python coding? : **I want to simplify the last bit of the code**

    UserSen = input("Enter a sentence of your choice, ")
    position = {} # word -> position
    words = UserSen.split()
    for word in words:
    if word not in position: # new word`
    position[word] = len(position) + 1 # store its position
    print(*map(position.__getitem__, word), sep=",")

**Just this print bit as I do not understand the "map", "getitem" and "sep" as I have not learnt this in school so it is irrelevant for me to use it.**    