Indexing routines

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])	Return an array representing the indices of a grid.
ix_(*args)	Construct an open mesh from multiple sequences.
ogrid	nd_grid 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 set 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.
lib.stride_tricks.as_strided(x[, shape, …])	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 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	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	Create nditers for use in nested loops
flatiter	Flat iterator object to iterate over arrays.
lib.Arrayterator(var[, buf_size])	Buffered iterator for big arrays.