Function stack

dask/array/_array_expr/_collection.py:1363–1453

Stack arrays along a new axis Given a sequence of dask arrays, form a new dask array by stacking them along a new dimension (axis=0 by default) Parameters ---------- seq: list of dask.arrays axis: int Dimension along which to align all of the arrays allow_u

(seq, axis=0, allow_unknown_chunksizes=False)

def stack(seq, axis=0, allow_unknown_chunksizes=False):
    """
    Stack arrays along a new axis

    Given a sequence of dask arrays, form a new dask array by stacking them
    along a new dimension (axis=0 by default)

    Parameters
    ----------
    seq: list of dask.arrays
    axis: int
        Dimension along which to align all of the arrays
    allow_unknown_chunksizes: bool
        Allow unknown chunksizes, such as come from converting from dask
        dataframes.  Dask.array is unable to verify that chunks line up.  If
        data comes from differently aligned sources then this can cause
        unexpected results.

    Examples
    --------

    Create slices

    >>> import dask.array as da
    >>> import numpy as np

    >>> data = [da.from_array(np.ones((4, 4)), chunks=(2, 2))
    ...         for i in range(3)]

    >>> x = da.stack(data, axis=0)
    >>> x.shape
    (3, 4, 4)

    >>> da.stack(data, axis=1).shape
    (4, 3, 4)

    >>> da.stack(data, axis=-1).shape
    (4, 4, 3)

    Result is a new dask Array

    See Also
    --------
    concatenate
    """
    from dask.array import wrap

    seq = [asarray(a, allow_unknown_chunksizes=allow_unknown_chunksizes) for a in seq]

    if not seq:
        raise ValueError("Need array(s) to stack")
    if not allow_unknown_chunksizes and not all(x.shape == seq[0].shape for x in seq):
        idx = first(i for i in enumerate(seq) if i[1].shape != seq[0].shape)
        raise ValueError(
            "Stacked arrays must have the same shape. The first array had shape "
            f"{seq[0].shape}, while array {idx[0] + 1} has shape {idx[1].shape}."
        )