Why equal variables are compared in Pandas Cython code?

Question

Looking at ewma method in https://github.com/pydata/pandas/blob/master/pandas/algos.pyx, there is a strange code:

for i from 1 <= i < N:
    cur = input[i]
    prev = output[i - 1]

    if **cur == cur:**
        if **prev == prev**:
            output[i] = oldw * prev + neww * cur
        else:
            output[i] = neww * cur
    else:
        output[i] = prev

Why is it comparing cur==cur and prev==prev?

I'm trying to implement this method in Java but get different results (7.01644573 in Python and 7.013072549019608 in Java, for example), so maybe this magic "==" operator does something?..

maybe [this](http://stackoverflow.com/questions/3437085/check-nan-number) is why — behzad.nouri, Dec 11 '13 at 15:10

Jeff · Accepted Answer · 2013-12-11T16:00:11.127

6

cur == cur will be True for all numbers / objects EXCEPT if cur is a np.nan essentially a quick way of nan testing

edited Dec 11 '13 at 16:00

answered Dec 11 '13 at 15:11

Jeff

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Why equal variables are compared in Pandas Cython code?

1 Answers1