ak.where
--------

.. py:module: ak.where

Defined in `awkward.operations.ak_where <https://github.com/scikit-hep/awkward/blob/e9dd2694cf5c6ccb1717358fe926816d8ecbfb9c/src/awkward/operations/ak_where.py>`__ on `line 19 <https://github.com/scikit-hep/awkward/blob/e9dd2694cf5c6ccb1717358fe926816d8ecbfb9c/src/awkward/operations/ak_where.py#L19>`__.

.. py:function:: ak.where(condition, *args, mergebool=True, highlevel=True, behavior=None, attrs=None)


    :param condition: Array-like data (anything :py:obj:`ak.to_layout` recognizes) of booleans.
    :param x: Optional array-like data (anything :py:obj:`ak.to_layout` recognizes) with the same
          length as ``condition``.
    :param y: Optional array-like data (anything :py:obj:`ak.to_layout` recognizes) with the same
          length as ``condition``.
    :param mergebool: If True, boolean and numeric data
                  can be combined into the same buffer, losing information about
                  False vs ``0`` and True vs ``1``; otherwise, they are kept in separate
                  buffers with distinct types (using an :py:obj:`ak.contents.UnionArray`).
    :type mergebool: bool, default is True
    :param highlevel: If True, return an :py:obj:`ak.Array`;
                  otherwise, return a low-level :py:obj:`ak.contents.Content` subclass.
    :type highlevel: bool, default is True
    :param behavior: Custom :py:obj:`ak.behavior` for the output array, if
                 high-level.
    :type behavior: None or dict
    :param attrs: Custom attributes for the output array, if
              high-level.
    :type attrs: None or dict

This function has a one-argument form, ``condition`` without ``x`` or ``y``, and
a three-argument form, ``condition``, ``x``, and ``y``. In the one-argument form,
it is completely equivalent to NumPy's
`nonzero <https://docs.scipy.org/doc/numpy/reference/generated/numpy.nonzero.html>`__
function.

In the three-argument form, it acts as a vectorized ternary operator:
``condition``, ``x``, and ``y`` must all have the same length and

.. code-block:: python


    output[i] = x[i] if condition[i] else y[i]

for all ``i``. The structure of ``x`` and ``y`` do not need to be the same; if
they are incompatible types, the output will have :py:obj:`ak.type.UnionType`.