What happens if you do arithmetic with NaN in Python?

python_math_isnan.ipynb

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      "#http://ludios.org/python-nan-equality-rules-and-cw-eq-equals/\n",
      "\n",
      "import math\n",
      "\n",
      "x= float('nan')\n",
      "y = float('nan') + 1\n",
      "math.isnan(x), math.isnan(y), x==y, x is y, x==x, [x] == [x]\n"
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