[Numpy-discussion] Does np.std() make two passes through the data?

Does np.std() make two passes through the data? Numpy:

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arr = np.random.rand(10) arr.std() 0.3008736260967052

Looks like an algorithm that makes one pass through the data (one for loop) wouldn't match arr.std():

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np.sqrt((arr*arr).mean() - arr.mean()**2) 0.30087362609670526

But a slower two-pass algorithm would match arr.std():

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np.sqrt(((arr - arr.mean())**2).mean()) 0.3008736260967052

Is there a way to get the same result as arr.std() in one pass (cython for loop) of the data?