issue_comments: 1062724755

OK, that is easy to change, now you have the exact same error message as for the appending. I have tried a lot of different ways and I am not getting anywhere with writing the data correctly in a store. ``` python import xarray as xr from rasterio.enums import Resampling import numpy as np

def init_coord(ds): ''' To have the geometry right''' arr_r=some_processing(ds.isel(time=slice(0,1))) return arr_r.x.values, arr_r.y.values

def some_processing(arr): ''' A reprojection routine''' arr = arr.rio.write_crs('EPSG:4326') arr_r = arr.rio.reproject('EPSG:3857', shape=(250, 250), resampling=Resampling.bilinear, nodata=np.nan) return arr_r

filename='processed_dataset.zarr' ds = xr.tutorial.open_dataset('air_temperature') x,y=init_coord(ds) ds_to_write=xr.Dataset(coords={'time':('time',ds.time.values),'x':('x', x),'y':('y',y)}) ds_to_write.to_zarr(filename, compute=False, encoding={"time": {"chunks": [1]}}) for i in range(len(ds.time)): # some kind of heavy processing arr_r=some_processing(ds.isel(time=slice(i,i+1))) buff= arr_r.drop(['spatial_ref','x','y']).chunk({'time':1,'x':250,'y':250}) buff.air.encoding['dtype']=np.dtype('float32') buff.to_zarr(filename, mode='a', region={'time':slice(i,i+1)}) ``ValueError: failed to prevent overwriting existing key _FillValue in attrs. This is probably an encoding field used by xarray to describe how a variable is serialized. To proceed, remove this key from the variable's attributes manually.`