Class VLArray

tables/vlarray.py:41–916

This class represents variable length (ragged) arrays in an HDF5 file. Instances of this class represent array objects in the object tree with the property that their rows can have a *variable* number of homogeneous elements, called *atoms*. Like Table datasets (see :ref:`TableClass

class VLArray(hdf5extension.VLArray, Leaf):
    """This class represents variable length (ragged) arrays in an HDF5 file.

    Instances of this class represent array objects in the object tree
    with the property that their rows can have a *variable* number of
    homogeneous elements, called *atoms*. Like Table datasets (see
    :ref:`TableClassDescr`), variable length arrays can have only one
    dimension, and the elements (atoms) of their rows can be fully
    multidimensional.

    When reading a range of rows from a VLArray, you will *always* get
    a Python list of objects of the current flavor (each of them for a
    row), which may have different lengths.

    This class provides methods to write or read data to or from
    variable length array objects in the file. Note that it also
    inherits all the public attributes and methods that Leaf (see
    :ref:`LeafClassDescr`) already provides.

    .. note::

          VLArray objects also support compression although compression
          is only performed on the data structures used internally by
          the HDF5 to take references of the location of the variable
          length data. Data itself (the raw data) are not compressed
          or filtered.

          Please refer to the `VLTypes Technical Note
          <https://support.hdfgroup.org/HDF5/doc/TechNotes/VLTypes.html>`_
          for more details on the topic.

    Parameters
    ----------
    parentnode
        The parent :class:`Group` object.
    name : str
        The name of this node in its parent group.
    atom
        An `Atom` instance representing the *type* and *shape* of the atomic
        objects to be saved.
    title
        A description for this node (it sets the ``TITLE`` HDF5 attribute on
        disk).
    filters
        An instance of the `Filters` class that provides information about the
        desired I/O filters to be applied during the life of this object.
    expectedrows
        A user estimate about the number of row elements that will
        be added to the growable dimension in the `VLArray` node.
        If not provided, the default value is ``EXPECTED_ROWS_VLARRAY``
        (see ``tables/parameters.py``).  If you plan to create either
        a much smaller or a much bigger `VLArray` try providing a guess;
        this will optimize the HDF5 B-Tree creation and management
        process time and the amount of memory used.

        .. versionadded:: 3.0

    chunkshape