The Index concept is implemented in 5 specialized classes:

  • ak.layout.Index64: values are 64-bit signed integers.

  • ak.layout.Index32: values are 32-bit signed integers.

  • ak.layout.IndexU32: values are 32-bit unsigned integers.

  • ak.layout.Index8: values are 8-bit signed integers.

  • ak.layout.IndexU8: values are 8-bit unsigned integers.

Index supports the buffer protocol, so it can be directly cast as a NumPy array.

An Index represents a contiguous, one-dimensional array of integers that is fully interpreted in the C++ layer. The structure of all ak.layout.Content nodes is implemented in Indexes, such as a ak.layout.ListArray’s starts and stops. Only data at the leaves of a structure, such as ak.layout.NumpyArray content, are not implemented in an Index. (This allows ak.layout.NumpyArray to handle non-contiguous, non-integer data.)

This distinction is made because the C++ layer needs to make stronger assumptions about the arrays used to define structure than any content at the leaves of the structure.



Creates an Index from a NumPy array. If the array has the wrong type for this specialization, or if it is not C-contiguous, the array is copied. Otherwise, it is a view (shares data).



Extracts one element from the Index.


ak.layout.Index.__getitem__(start, stop)

Slices the Index between start and stop.



The length of the Index.



A string representation of the Index (single-line XML, trucated middle).