Python - Game stat calculator

Question

So this is the code to a calculator I made for a game. Essentially what the calculator does is, it calculates the cost of buying the next stat.

So I wrote the code just for the Human race and the strength stat. From the way I see it, I will have to do for each race the same code 3 times for each stat.

I was hoping there would be a shorter way around this like

instead of human.strength I would like it to be race.strength where race = user_race.

Thanks

class race:
    """The different races in the calculator"""
    def __init__(self, race, strength, agility, health, strength_cost, agility_cost, health_cost):
        self.race = race
        self.strength = strength
        self.agility = agility
        self.health = health
        self.strength_cost = strength_cost
        self.agility_cost = agility_cost
        self.health_cost = health_cost

human = race('Human', 15, 17, 18, 5, 3, 4) 
elf = race('Elf', 11, 21, 14, 4, 3, 5)
giant = race('Giant', 25, 11, 27, 4, 8, 3)

print("Human, Giant, Elf")
user_race = str(input("Enter your race:")).lower()
print("Strength, Agility, Health")
user_stat = str(input("Enter your desired stat:")).lower()
user_present_stat_value = int(input("Enter your present stat value:"))
user_desired_stat_value = int(input("Enter your desired stat value:"))

if user_race == 'human' and user_stat == 'strength':
    human_strength_present_statdif = (user_present_stat_value - human.strength) # difference of present stat with respect of base stat

    human_strength_desired_statdif = (user_desired_stat_value - human.strength) #difference of desired stat with respect of base stat
    
    human_strength_present_stat_cost = (human.strength_cost + (human_strength_present_statdif - 1) * human.strength_cost) #The cost of present stat stat 
    
    human_strength_total_present_cost = ((human_strength_present_statdif / 2) * (human.strength_cost + human_strength_present_stat_cost)) # The total cost from base stat to present stat
    
    human_strength_desired_stat_cost = (human.strength_cost + (human_strength_desired_statdif - 1) * human.strength_cost) #The cost of desired stat
    
    human_strength_total_desired_cost = ((human_strength_desired_statdif / 2) * (human.strength_cost + human_strength_desired_stat_cost)) # The total cost base stat to desired stat
    
    human_strength_net_cost = (human_strength_total_desired_cost - human_strength_total_present_cost) # The Net cost from the difference of Total desired stat and Total present stat
    
    print("Net cost: " + str(human_strength_net_cost))
```

Answer 1

If you are just trying to make an interactive calculator, the classes, etc. are not needed.

First, make a simple table that lets you look up the stats based on race. Keep it easy for a human (like you) to edit it, make changes, add new races or stats, etc.

keys = "base_strength base_agility base_health strength_cost agility_cost health_cost".split()

traits = [
    #        base     base    base  strength agility health 
    #race  strength agility  health   cost     cost   cost
    "human    15       17      18      5        3      4",
    "elf      11       21      14      4        3      5",
    "giant    25       11      27      4        8      3",
]

It's just a list of strings. Now transform it into a format that makes it easy to use in a program. We'll turn it into a dict of dicts so we can look up values using something like: stat["elf"]["base_agility"]. Here's the code:

stats = {}

for row in traits:
    row = row.strip().split()
    stats[row[0]] = dict(zip(keys, map(int, row[1:])))

Now your code that calculates the cost of changing strength for a human, can be turned into a generic function that works for any race or stat:

def calc_change_cost(race, stat_name, present_value, desired_value):
    base_value = stats[race][f"base_{stat_name}"]
    stat_cost = stats[race][f"{stat_name}_cost"]

    present_statdif = present_value - base_value
    present_stat_cost = stat_cost + (present_statdif - 1) * stat_cost
    total_present_cost = (present_statdif / 2) * (stat_cost + present_stat_cost)

    desired_statdif = desired_value - base_value
    desired_stat_cost = stat_cost + (desired_statdif - 1) * stat_cost
    total_desired_cost = (desired_statdif / 2) * (stat_cost + desired_stat_cost)

    net_cost = total_desired_cost - total_present_cost

    return net_cost

You'll notice the repeated code for calculating total_present_cost and total_desired_cost. Those lines could be refactored into another function (an exercise for the reader).

Now, the main program just collects the user's inputs, calls the function above, and prints the results:

user_race = str(input("Enter your race (Human, Giant, Elf):")).lower()
user_stat = str(input("Enter your desired stat (Strength, Agility, Health):")).lower()
present_value = int(input("Enter your present stat value:"))
desired_value = int(input("Enter your desired stat value:"))

net_cost = calc_change_cost(user_race, user_stat, present_value, desired_value)
print(f"Net cost to change {user_race} {user_stat} from {present_value} to {desired_value}: {net_cost}")