How to duplicate Matlab functionality

Since I am a total Matlab-n00b, I rather write a convoluted Python script instead of using the appropriate Matlab function. And here it is. A small script to compute the standard deviation of two vectors. I guess this would have been one Matlab command.

import sys
import math

def computeStdDev(file, vec1, vec2):
data =, struct_as_record=True)
vector1 = data[vec1]
vector2 = data[vec2]
if len(vector1) != len(vector2):
print "Error: Vectors do not have matching lengths."
diff = vector1
N = len(diff)

for i in range(N):
diff[i] = vector1[i] - vector2[i]

mu = 0
for val in diff:
mu = mu + val
mu = mu / float(N)

sigma = 0
for i in range(N):
sigma = sigma + (diff[i] - mu)**2
sigma = math.sqrt(sigma / float(N))

print "mu: %f" % mu
print "sigma: %f" % sigma

if len(sys.argv) != 4:
print "Usage: %s file vector1 vector2" % sys.argv[0]

computeStdDev(sys.argv[1], sys.argv[2], sys.argv[3])