How do I use an accumulator with a for loop range in Python?

Question

I am trying to use an accumulator in Python but I cannot get it to work. I want the population to start out at 2 and increase by the percentIncrease input but it is not coming out correctly. What am I doing wrong? I know it is how I am accumulating it but every attempt I have tried has failed.

#Get the starting number of organisms
startingNum = int(input('Enter the starting number of organisms:'))

#Get the average daily increase
percentIncrease = float(input('Enter the percentage of average daily increase of organisms:'))

#Get the number of days to multiply
number_of_Days = int(input('Enter the number of days to multiply:'))

population = 0
cumPopulation = 0

for number_of_Days in range(1,number_of_Days + 1):
    population = startingNum
    cumPopulation += population *(1+percentIncrease)
    print(number_of_Days,'\t',cumPopulation)


#So inputs of 2, .3, and 10 should become:
1   2
2   2.6
3   3.38
4   4.394
5   5.7122
6   7.42586
7   9.653619
8   12.5497
9   16.31462
10  21.209

Answer 1

Not sure do you need to print day 1 as the startingNum or day 1 as startingNum * (1+ percentIncrease).

This is what you want:

#Get the starting number of organisms
startingNum = int(input('Enter the starting number of organisms:'))

#Get the average daily increase
percentIncrease = float(input('Enter the percentage of average daily increase of organisms:'))

#Get the number of days to multiply
number_of_Days = int(input('Enter the number of days to multiply:'))

printFormat = "Day {}\t Population:{}" 
cumPopulation = startingNum

print(printFormat.format(1,cumPopulation))

for number_of_Days in range(number_of_Days):
    cumPopulation *=(1+percentIncrease) # This equals to cumPopulation = cumPopulation * (1 + percentIncrease)
    print(printFormat.format(number_of_Days+2,cumPopulation))

Output:

Enter the starting number of organisms:100
Enter the percentage of average daily increase of organisms:0.2
Enter the number of days to multiply:10
Day 1    Population:100
Day 2    Population:120.0
Day 3    Population:144.0
Day 4    Population:172.8
Day 5    Population:207.36
Day 6    Population:248.832
Day 7    Population:298.5984
Day 8    Population:358.31808
Day 9    Population:429.981696
Day 10   Population:515.9780352
Day 11   Population:619.17364224