import dask
import dask.array as da

arr = da.from_array([1, 1, 1, 2, 3, 4, 4])

unique, counts = da.unique(arr, return_counts=True)

unique, counts = dask.compute(unique, counts)
result = dict(zip(unique, counts))
# {1: 3, 2: 1, 3: 1, 4: 2}