how to implement the input of variables by keyboard in python?

how to implement the input of variables by keyboard in the next python program that calculates resistances in parallel?

# 1/R = 1/R1 + 1/R2 + 1/R3 +.....+ 1/Rn
class ParallelResistance: # class ParallelResistance
# this function calculate the resistance in parallel
    def calculate(self, *agrs):
        total = 0 # taking total resistance as 0
        for resistance in agrs:
# calculating 1/R1 + 1/R2 + 1/R3 +.....+ 1/Rn
            total = total + 1/resistance
        result = 1/total # calculate 1/R
        return round(result, 2) # return the total resistance in parallel

parallel = ParallelResistance() # creating a instance of ParallelResistance class
print("The resistance in parallel is: ")
print(parallel.calculate(200,470,220)) # calling the calculate method of ParallelResistance class