# Program to compute the mean and variance of some numbers
# (user enters number of numbers, then numbers)
# Matt Bishop, COSMOS 2012, Cluster 4

# compute the mean and variancen of the numbers
# parameter: listnum, a list of numbers
def stats(listnum):
    # initialize sum
    sum = 0
    # add each number in list to sum
    for i in listnum:
        sum += i
    # get average
    avg = sum / len(listnum)
    # now get the sum of the squares of the differences
    vartop = 0.0
    for i in listnum:
        vartop += (i - avg) ** 2
    # now, the actual variance
    var = vartop / len(listnum)
    return avg, var
    


# read a list of numbers and print the mean and variance
# calls: function mean, stdev
def main():
    # prompt for count of numbers to be entered
    try:
        n = int(input("How many numbers do you want to add? "))
    except:
        print("Please enter an integer")
        return
    # error check
    if n < 0:
        print("Please enter a positive integer")
        return
    # if n is 0, there is nothing to do
    if n == 0:
        print("The mean and variance of your numbers are 0")
        return
    # we have some numbers to add -- do it!
    # initialize list variable
    numbers = []
    # ask user for next number and
    # append each number to the list
    i = 1
    while i <= n:
        prompt = "Enter number %d: " % i
        try:
            k = int(input(prompt))
        except:
            print("Oops . . . that's not an integer . . . try again")
        else:
            numbers = numbers + [ k ]
            i += 1
    # print the statistics
    mean, variance = stats(numbers)
    # print the standard deviation
    print("The mean of your numbers is", mean, "and the variance is", variance)

main()