da_block_slow.py

import time
import uuid
import numpy as np
import dask.array as da


class ArrayLikeObject:

    def __init__(self):
        self._array = np.ones((20, 30), dtype=float)

    def __getitem__(self, item):
        return self._array[item]

    @property
    def shape(self):
        return self._array.shape

    @property
    def ndim(self):
        return self._array.ndim

    @property
    def size(self):
        return self._array.size

    @property
    def dtype(self):
        return self._array.dtype


meta = np.zeros((0,), dtype=float)

start = time.time()
chunks = [[[[da.from_array(ArrayLikeObject(), name=str(uuid.uuid4()), meta=meta)] * 269] * 6] * 4]
print(time.time() - start)
data = da.block(chunks)
print(time.time() - start)
print(data)

When I run this I get:

dask.array<concatenate, shape=(1, 4, 120, 8070), dtype=float64, chunksize=(1, 1, 20, 30), chunktype=numpy.ndarray>

the shape is wrong?