Python program to find standard deviation

So here is the function code:

def stdv(X):
    mean = sum(X)/len(X)
    tot = 0.0
    for x in X:
        tot = tot + (x - mean)**2
    return (tot/len(X))**0.5

# main code
#  a simple data-set 
sample = [1, 2, 3, 4, 5] 
print("Standard Deviation of the sample is: ", stdv(sample))

sample = [1, 2, 3, -4, -5] 
print("Standard Deviation of the sample is: ", stdv(sample))

sample = [10, -20, 30, -40, 50] 
print("Standard Deviation of the sample is: ", stdv(sample))

Output:

Standard Deviation of the sample is:  1.4142135623730951 
Standard Deviation of the sample is:  3.2619012860600183 
Standard Deviation of the sample is:  32.61901286060018