Wrong sum of boolean negation about xarray HOT 3 CLOSED

Thanks so much for explaining this in detail, @Ockenfuss and my apologies for taking up your time! I thought the expression would evaluate from left to right. Using np.logical_not() is a great suggestion.

from xarray.

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This is actually expected behaviour in python. If you do ~test.sum(dim="x"), the call to sum() has a higher precedence than the bitwise invert operator, represented by ~. Therefore, test.sum(dim='x') evaluates to 2 and then ~2 evaluates to -3. The latter is due to the way integers are represented as bits in python.

In general, it might be better to use np.logical_not(test) in order to invert the array. logical_not also works in case your data consists of integers instead of booleans:

import numpy as np
import xarray as xr

data_int=np.array([1, 0, 1, 0])
test_int=xr.DataArray(data_int, coords=dict(x=np.arange(4)))
assert np.logical_not(test_int).sum(dim='x')==2 #works
assert (~test_int).sum(dim='x')==2 #fails

from xarray.