statistical operations

#sum
def x_sum(x_input):
    x = 0 
    for each in x_input:
        x += each
    return x
    
#average
def x_average(x_input):
    x = x_sum(x_input)/float(len(x_input))
    return x
    
#variance
def x_variance(x_input):
    num = len(x_input)
    average = x_average(x_input)
    variance = 0
    for x in x_input:
        variance += float(average - x) ** 2
    return variance/num

#standard deviation
def x_std_deviation(variance):
    return variance ** 0.5

variance = x_variance(x_input)

print x_std_deviation(variance)
print x_sum(x_input)
print x_average(x_input)