hub.core.index

class hub.core.index.IndexEntry(value: Union[int, slice, Tuple[int]] = slice(None, None, None))

__getitem__(item: Union[int, slice, Tuple[int]])

Combines the given item and this IndexEntry. Returns a new IndexEntry representing the composition of the two.

Examples

>>> IndexEntry()[0:100]
IndexEntry(slice(0, 100, None))

>>> IndexEntry()[100:200][5]
IndexEntry(105)

>>> IndexEntry()[(0, 1, 2, 3)]
IndexEntry((0, 1, 2, 3))

>>> IndexEntry()[1, 2, 3]
IndexEntry((0, 1, 2, 3))

Parameters: item – The desired sub-index to be composed with this IndexEntry. Can be an int, a slice, or a tuple of ints.
Returns: The new IndexEntry object.
Return type: IndexEntry
Raises: TypeError – An integer IndexEntry should not be indexed further.

__init__(value: Union[int, slice, Tuple[int]] = slice(None, None, None))

__str__(): Return str(self).

__weakref__: list of weak references to the object (if defined)

indices(length: int): Generates the sequence of integer indices for a target of a given length.

is_trivial(): Checks if an IndexEntry represents the entire slice

length(parent_length: int) → int

Returns the length of an IndexEntry given the length of the parent it is indexing.

Examples

>>> IndexEntry(slice(5, 10)).length(100)
5
>>> len(list(range(100))[5:10])
5
>>> IndexEntry(slice(5, 100)).length(50)
45
>>> len(list(range(50))[5:100])
45
>>> IndexEntry(0).length(10)
1

Parameters: parent_length (int) – The length of the target that this IndexEntry is indexing.
Returns: The length of the index if it were applied to a parent of the given length.
Return type: int

subscriptable(): Returns whether an IndexEntry can be further subscripted.

validate(parent_length: int): Checks that the index is not accessing values outside the range of the parent.

class hub.core.index.Index(item: Union[int, slice, Tuple[int], Index, List[IndexEntry]] = slice(None, None, None))

__getitem__(item: Union[int, slice, List[int], Tuple[Union[int, slice, Tuple[int]]], Index])

Returns a new Index representing a subscripting with the given item. Modeled after NumPy’s advanced integer indexing.

See: https://numpy.org/doc/stable/reference/arrays.indexing.html

Examples

>>> Index([5, slice(None)])[5]
Index([5, 5])

>>> Index([5])[5:6]
Index([5, slice(5, 6)])

>>> Index()[0, 1, 2:5, 3]
Index([0, 1, slice(2, 5), 3])

>>> Index([slice(5, 6)])[(0, 1, 2:5, 3),]
Index([(5, 1, slice(2, 5), 3)])

Parameters: item – The contents of the subscript expression to add to this Index.
Returns: The Index representing the result of the subscript operation.
Return type: Index
Raises: TypeError – Given item should be another Index, or compatible with NumPy’s advanced integer indexing.

__init__(item: Union[int, slice, Tuple[int], Index, List[IndexEntry]] = slice(None, None, None))

Initializes an Index from an IndexValue, another Index, or the values from another Index.

Represents a list of IndexEntry objects corresponding to indexes into each axis of an ndarray.

__repr__(): Return repr(self).

__str__(): Return str(self).

__weakref__: list of weak references to the object (if defined)

apply(samples: List[ndarray]): Applies an Index to a list of ndarray samples with the same number of entries as the first entry in the Index.

apply_squeeze(samples: List[ndarray]): Applies the primary axis of an Index to a list of ndarray samples. Will either return the list as given, or return the first sample.

compose_at(item: Union[int, slice, Tuple[int]], i: Optional[int] = None)

Returns a new Index representing the addition of an IndexValue, or the composition with a given axis.

Examples

>>> Index([slice(None), slice(None)]).compose_at(5)
Index([slice(None), slice(None), 5])

>>> Index([slice(None), slice(5, 10), slice(None)]).compose_at(3, 1)
Index([slice(None), 8, slice(None)])

Parameters

item (IndexValue) – The value to append or compose with the Index.
i (int, optional) – The axis to compose with the given item. Defaults to None, meaning that the item will be appended instead.

Returns

The result of the addition or composition.

Return type

Index

find_axis(offset: int = 0)

Returns the index for the nth subscriptable axis in the values of an Index.

Parameters: offset (int) – The number of subscriptable axes to skip before returning. Defaults to 0, meaning that the first valid axis is returned.
Returns: The index of the found axis, or None if no match is found.
Return type: int

is_trivial(): Checks if an Index is equivalent to the trivial slice [:], aka slice(None).

length(parent_length: int): Returns the primary length of an Index given the length of the parent it is indexing. See: IndexEntry.length()

validate(parent_length): Checks that the index is not accessing values outside the range of the parent.

hub.core.index.merge_slices(existing_slice: slice, new_slice: slice) → slice

Compose two slice objects

Given an iterable x, the following should be equivalent:

x[existing_slice][new_slice] == x[merge_slices(existing_slice, new_slice)]

Parameters

existing_slice (slice) – The existing slice to be restricted.
new_slice (slice) – The new slice to be applied to the existing slice.

Returns

the composition of the given slices

Return type

slice

Raises

NotImplementedError – Composing slices with negative values is not supported. Negative indexing for slices is only supported for the first slice.

hub.core.index.slice_at_int(s: slice, i: int)

Returns the i th element of a slice s.

Examples

>>> slice_at_int(slice(None), 10)
10

>>> slice_at_int(slice(10, 20, 2), 3)
16

Parameters

s (slice) – The slice to index into.
i (int) – The integer offset into the slice.

Returns

The index corresponding to the offset into the slice.

Return type

int

Raises

NotImplementedError – Nontrivial slices should not be indexed with negative integers.
IndexError – If step is negative and start is not greater than stop.

hub.core.index.slice_length(s: slice, parent_length: int) → int: Returns the length of a slice given the length of its parent.