ak.firsts — Awkward Array documentation

# ak.firsts

Defined in awkward.operations.structure on line 3055.

ak.firsts(array, axis=1, highlevel=True, behavior=None)
  Parameters:

    - array – Data from which to select the first elements from nested lists.

    - axis (int) – The dimension at which this operation is applied. The outermost dimension is `0`, followed by `1`, etc., and negative values count backward from the innermost: `-1` is the innermost dimension, `-2` is the next level up, etc.

    - highlevel (bool) – If True, return an `ak.Array`; otherwise, return a low-level `ak.layout.Content` subclass.

    - behavior (None or dict) – Custom `ak.behavior` for the output array, if high-level.

Selects the first element of each non-empty list and inserts None for each empty list.

For example,

    >>> array = ak.Array([[1.1], [2.2], [], [3.3], [], [], [4.4], [5.5]])
    >>> print(ak.firsts(array))
    [1.1, 2.2, None, 3.3, None, None, 4.4, 5.5]

See `ak.singletons` to invert this function.