ak.layout.RegularArray¶
The RegularArray class describes lists that all have the same length, the single
integer size. Its underlying content is a flattened view of the data;
that is, each list is not stored separately in memory, but is inferred as a
subinterval of the underlying data.
If the content length is not an integer multiple of size, then the length
of the RegularArray is truncated to the largest integer multiple.
An extra field zeros_length is ignored unless the size is zero. This sets the
length of the RegularArray in only those cases, so that it is possible for an
array to contain a non-zero number of zero-length lists with regular type.
A multidimensional ak.layout.NumpyArray is equivalent to a one-dimensional ak.layout.NumpyArray nested within several RegularArrays, one for each dimension. However, RegularArrays can be used to make lists of any other type.
RegularArray corresponds to an Apache Arrow Tensor.
Below is a simplified implementation of a RegularArray class in pure Python
that exhaustively checks validity in its constructor (see
ak.is_valid) and can generate random valid arrays. The
random_number() function returns a random float and the
random_length(minlen) function returns a random int that is at least
minlen. The RawArray class represents simple, one-dimensional data.
class RegularArray(Content):
def __init__(self, content, size, zeros_length=0):
assert isinstance(content, Content)
assert isinstance(size, int)
assert isinstance(zeros_length, int)
assert size >= 0
if size != 0:
length = len(self.content) // self.size # floor division
else:
assert zeros_length >= 0
length = zeros_length
self.content = content
self.size = size
self.length = length
@staticmethod
def random(minlen, choices):
size = random_length(0, 5)
zeros_length = random_length(0, 5)
content = random.choice(choices).random(random_length(minlen) * size, choices)
return RegularArray(content, size, zeros_length)
def __len__(self):
return self.length
def __getitem__(self, where):
if isinstance(where, int):
assert 0 <= where < len(self)
return self.content[(where) * self.size:(where + 1) * self.size]
elif isinstance(where, slice) and where.step is None:
start = where.start * self.size
stop = where.stop * self.size
zeros_length = where.stop - where.start
return RegularArray(self.content[start:stop], self.size, zeros_length)
elif isinstance(where, str):
return RegularArray(self.content[where], self.size, self.length)
else:
raise AssertionError(where)
def __repr__(self):
if size == 0:
zeros_length = ", " + repr(self.length)
else:
zeros_length = ""
return "RegularArray(" + repr(self.content) + ", " + repr(self.size) + zeros_length + ")"
def xml(self, indent="", pre="", post=""):
out = indent + pre + "<RegularArray>\n"
out += self.content.xml(indent + " ", "<content>", "</content>\n")
out += indent + " <size>" + str(self.size) + "</size>\n"
if size == 0:
out += indent + " <zeros_length>" + str(self.length) + "</zeros_length>\n"
out += indent + "</RegularArray>" + post
return out
Here is an example:
RegularArray(RawArray([7.4, -0.0, 6.6, 6.6, 5.2, 4.6, 9.6, 4.2, 2.3, 6.5, 4.2, 1.3, 2.2, 4.1,
1.9, 3.9, 2.3, 2.3, 0.7, 6.9, 1.4, 9.6, 11.8, 6.8, 8.2, 10.5, 8.2,
7.5, 6.3, 5.4, 0.5, 1.0, 5.5, 4.1, 5.9, 7.9, 6.7, 7.3, 5.6, 5.5, 2.2,
2.2, -0.3, 3.5, 11.2, 13.4, 6.7, -1.0, 6.4, 1.3, 6.8, 5.1, 3.2, 9.5,
2.8]),
5)
<RegularArray>
<content><RawArray>
<ptr>7.4 -0.0 6.6 6.6 5.2 4.6 9.6 4.2 2.3 6.5 4.2 1.3 2.2 4.1 1.9 3.9 2.3 2.3 0.7 6.9
1.4 9.6 11.8 6.8 8.2 10.5 8.2 7.5 6.3 5.4 0.5 1.0 5.5 4.1 5.9 7.9 6.7 7.3 5.6
5.5 2.2 2.2 -0.3 3.5 11.2 13.4 6.7 -1.0 6.4 1.3 6.8 5.1 3.2 9.5 2.8</ptr>
</RawArray></content>
<size>5</size>
</RegularArray>
which represents the following logical data.
[[7.4, -0.0, 6.6, 6.6, 5.2],
[4.6, 9.6, 4.2, 2.3, 6.5],
[4.2, 1.3, 2.2, 4.1, 1.9],
[3.9, 2.3, 2.3, 0.7, 6.9],
[1.4, 9.6, 11.8, 6.8, 8.2],
[10.5, 8.2, 7.5, 6.3, 5.4],
[0.5, 1.0, 5.5, 4.1, 5.9],
[7.9, 6.7, 7.3, 5.6, 5.5],
[2.2, 2.2, -0.3, 3.5, 11.2],
[13.4, 6.7, -1.0, 6.4, 1.3],
[6.8, 5.1, 3.2, 9.5, 2.8]]
In addition to the properties and methods described in ak.layout.Content, a RegularArray has the following.
ak.layout.RegularArray.__init__¶
-
ak.layout.RegularArray.__init__(content, size, identities=None, parameters=None)¶
ak.layout.RegularArray.compact_offsets64¶
-
ak.layout.RegularArray.compact_offsets64(start_at_zero=True)¶
Returns a 64-bit ak.layout.Index of offsets by prefix summing
in steps of size.
ak.layout.RegularArray.broadcast_tooffsets64¶
-
ak.layout.RegularArray.broadcast_tooffsets64(offsets)¶
Shifts contents to match a given set of offsets (if possible) and
returns a ak.layout.ListOffsetArray with the results. This is used in
broadcasting because a set of ak.types.ListType and ak.types.RegularType
arrays have to be reordered to a common offsets before they can be directly
operated upon.