# Need to be helped: stuck on loops and functions from beginner class :(

I don't know what is wrong with my code.

Here is the question:

Part C: Finding the right amount to save away ​Please In Part B, you had a chance to explore how both the percentage of your salary that you save each month and your annual raise affect how long it takes you to save for a down payment. This is nice, but suppose you want to set a particular goal, e.g. to be able to afford the down payment in three years. How much should you save each month to achieve this? In this problem, you are going to write a program to answer that question. To simplify things, assume:

1. Your semi­annual raise is .07 (7%)
2. Your investments have an annual return of 0.04 (4%)
3. The down payment is 0.25 (25%) of the cost of the house
4. The cost of the house that you are saving for is \$1M.

You are now going to try to find the best rate of savings to achieve a down payment on a \$1M house in 36 months. Since hitting this exactly is a challenge, we simply want your savings to be within \$100 of the required down payment. In​ ps1c.py​, write a program to calculate the best savings rate, as a function of your starting salary. You should use ​bisection search​ to help you do this efficiently. You should keep track of the number of steps it takes your bisections search to finish. You should be able to reuse some of the code you wrote for part B in this problem. Because we are searching for a value that is in principle a float, we are going to limit ourselves to two decimals of accuracy (i.e., we may want to save at 7.04% ­­ or 0.0704 in decimal – but we are not going to worry about the difference between 7.041% and 7.039%). This means we can search for an integer​ between 0 and 10000 (using integer division), and then convert it to a decimal percentage (using float division) to use when we are calculating the ​current_savings​ after 36 months. By using this range, there are only a finite number of numbers that we are searching over, as opposed to the infinite number of decimals between 0 and 1. This range will help prevent infinite loops. The reason we use 0 to 10000 is to account for two additional decimal places in the range 0% to 100%. Your code should print out a decimal (e.g. 0.0704 for 7.04%).

Try different inputs for your starting salary, and see how the percentage you need to save changes to reach your desired down payment. Also keep in mind it may not be possible for to save a down payment in a year and a half for some salaries. In this case your function should notify the user that it is not possible to save for the down payment in 36 months with a print statement. ​Please make your program print results in the format shown in the test cases below. Note: There are multiple right ways to implement bisection search/number of steps so your results may not perfectly match those of the test case.

Hints:

● There may be multiple savings rates that yield a savings amount that is within \$100 of the required down payment on a \$1M house. In this case, you can just return any of the possible values.

● Depending on your stopping condition and how you compute a trial value for bisection search, your number of steps may vary slightly from the example test cases.

● Watch out for integer division when calculating if a percentage saved is appropriate and when calculating final decimal percentage savings rate.

● Remember to reset the appropriate variable(s) to their initial values for each iteration of bisection search.

I am python beginner and working on this assignment, but there are somethings wrong with my code. I am stuck with the bisection search. Hope you guys could give me any help, very appreciated it.

Here is my code:

``````annual_salary = float(input("Enter your annual salary: "))
month_salary = annual_salary/12
total_cost = 1000000
down_payment = total_cost * 0.25
semi_annual_rate = 0.07
investment_rate = 0.04
high = 1.0
low = 0
guess = (high+low)/2
current_savings = 0
steps = 0
month = 0

#calculate current_savings
def cal_current_savings(current_savings, month_salary, guess, month):
for month in range(37):
if month % 6 == 1:
month_salary = month_salary * semi_annual_rate + month_salary
current_savings = current_savings + month_salary * guess
current_savings = current_savings * (1+0.04)
return(current_savings)

#count times of guessing
while abs(current_savings - down_payment) >= 100:
current_savings = cal_current_savings(current_savings, month_salary, guess, ,month)
if current_savings < down_payment:
low = guess
current_savings = 0
else:
high = guess
current_savings = 0
guess = (high+low)/2
steps = steps + 1
if steps > 200:
break

#outputs
print ("Best savings rate: ", guess)
print ("Steps in bisection search: ", steps)
``````