def calc_prof(ability, profs, prof_bonus):
    """
    Determine if proficiency modifier needs to be applied.
    If character has expertise in selected skill, double the proficiency bonus.
    If character has proficiency in selected skill/ability/save,
        prof_mod = prof_bonus (multiply by 1).
    If character has no proficiency in selected skill/ability/save,
        prof_mod = 0 (no bonus).
    """
    if ability in profs.keys():
        prof_mod = profs[ability] * int(prof_bonus)
    else:
        prof_mod = 0

    return prof_mod