Indexing routines

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NumPy API Reference: Indexing routines

Generating index arrays

c_
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nonzero(a)	Return the indices of the elements that are non-zero.
where(condition[, x, y])	Return elements, either from x or y, depending on condition.
indices(dimensions[, dtype])	Returns an array representing the indices of a grid.
mask_indices(n, mask_func[, k])	Return the indices to access (n, n) arrays, given a masking function.
tril_indices(n[, k, m])	Returns the indices of the lower triangular matrix.
tril_indices_from(arr[, k])	Returns the indices for the lower-triangle of arr.
triu_indices(n[, k, m])	Returns the indices of the upper triangular matrix.
triu_indices_from(arr[, k])	Returns indices for the upper-triangle of arr.
ix_(*args)	Construct an open mesh from multiple sequences.
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, dims[, order])	Converts 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.

Indexing-like operations

take(a, indices[, axis, out])	Takes elements of an array at specified indices along an axis.
take_along_axis(a, indices, axis)	Take values from the input array by matching 1d index and data slices.
choose(a, choices[, out, mode])
compress(condition, a[, axis, out])	Returns selected slices of an array along given axis.
diag(v[, k])	Returns a diagonal or a diagonal array.
diagonal(a[, offset, axis1, axis2])	Returns specified diagonals.
select(condlist, choicelist[, default])	Return an array drawn from elements in choicelist, depending on conditions.
lib.stride_tricks.as_strided(x[, shape, strides])	Create a view into the array with the given shape and strides.

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 inplace, based on a conditional mask and input values.
fill_diagonal(a, val[, wrap])	Fills the main diagonal of the given array of any dimensionality.

Iterating over arrays

flatiter(a)

Flat iterator object to iterate over arrays.