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# Indexing routines

See also

Indexing on ndarrays

## Generating index arrays

`c_` | Translates slice objects to concatenation along the second axis.
`r_` | Translates slice objects to concatenation along the first axis.
`s_` | A nicer way to build up index tuples for arrays.
`nonzero`(a) | Return the indices of the elements that are non-zero.
`where`(condition, [x, y], /) | Return elements chosen from x or y depending on condition.
`indices`(dimensions[, dtype, sparse]) | Return an array representing the indices of a grid.
`ix_`(*args) | Construct an open mesh from multiple sequences.
`ogrid` | An instance which returns an open multi-dimensional "meshgrid".
`ravel_multi_index`(multi_index, dims[, mode, ...]) | Converts a tuple of index arrays into an array of flat indices, applying boundary modes to the multi-index.
`unravel_index`(indices, shape[, order]) | Converts a flat index or array of flat indices into a tuple of coordinate arrays.
`diag_indices`(n[, ndim]) | Return the indices to access the main diagonal of an array.
`diag_indices_from`(arr) | Return the indices to access the main diagonal of an n-dimensional array.
`mask_indices`(n, mask_func[, k]) | Return the indices to access (n, n) arrays, given a masking function.
`tril_indices`(n[, k, m]) | Return the indices for the lower-triangle of an (n, m) array.
`tril_indices_from`(arr[, k]) | Return the indices for the lower-triangle of arr.
`triu_indices`(n[, k, m]) | Return the indices for the upper-triangle of an (n, m) array.
`triu_indices_from`(arr[, k]) | Return the indices for the upper-triangle of arr.

## Indexing-like operations

`take`(a, indices[, axis, out, mode]) | Take elements from an array along an axis.
`take_along_axis`(arr, indices[, axis]) | Take values from the input array by matching 1d index and data slices.
`choose`(a, choices[, out, mode]) | Construct an array from an index array and a list of arrays to choose from.
`compress`(condition, a[, axis, out]) | Return selected slices of an array along given axis.
`diag`(v[, k]) | Extract a diagonal or construct a diagonal array.
`diagonal`(a[, offset, axis1, axis2]) | Return specified diagonals.
`select`(condlist, choicelist[, default]) | Return an array drawn from elements in choicelist, depending on conditions.

## Inserting data into arrays

`place`(arr, mask, vals) | Change elements of an array based on conditional and input values.
`put`(a, ind, v[, mode]) | Replaces specified elements of an array with given values.
`put_along_axis`(arr, indices, values, axis) | Put values into the destination array by matching 1d index and data slices.
`putmask`(a, /, mask, values) | Changes elements of an array based on conditional and input values.
`fill_diagonal`(a, val[, wrap]) | Fill the main diagonal of the given array of any dimensionality.

## Iterating over arrays

`nditer`(op[, flags, op_flags, op_dtypes, ...]) | Efficient multi-dimensional iterator object to iterate over arrays.
`ndenumerate`(arr) | Multidimensional index iterator.
`ndindex`(*shape) | An N-dimensional iterator object to index arrays.
`nested_iters`(op, axes[, flags, op_flags, ...]) | Create nditers for use in nested loops
`flatiter`() | Flat iterator object to iterate over arrays.
`iterable`(y) | Check whether or not an object can be iterated over.