# Finding the Variance and Standard Deviation of a list of numbers

def calculate_mean(n):
    s = sum(n)
    N = len(n)
    # Calculate the mean
    mean = s / N 
    return mean 

def find_differences(n):
    #Find the mean
    mean = calculate_mean(n)
    # Find the differences from the mean
    diff = []
    for num in n:
        diff.append(num-mean)
    return diff

def calculate_variance(n):
    diff = find_differences(n)
    squared_diff = []
    # Find the squared differences
    for d in diff:
        squared_diff.append(d**2)
    # Find the variance
    sum_squared_diff = sum(squared_diff)
    variance = sum_squared_diff / len(n)
    return variance

if __name__ == '__main__':
    donations = [100, 60, 70, 900, 100, 200, 500, 500, 503, 600, 1000, 1200]
    variance = calculate_variance(donations)
    print('The variance of the list of numbers is {0}'.format(variance))
    
    std = variance ** 0.5
    print('The standard deviation of the list of numbers is {0}'.format(std))
#src : Doing Math With Python