ak.layout.ByteMaskedArray¶
The ByteMaskedArray implements an ak.types.OptionType with two aligned
arrays, a boolean mask and content. At any element i where
mask[i] == valid_when, the value can be found at content[i]. If
mask[i] != valid_when, the value is missing (None).
This is equivalent to NumPy’s
masked arrays
if valid_when=False.
There is no Apache Arrow equivalent because Arrow uses bitmaps to mask all node types.
Below is a simplified implementation of a ByteMaskedArray 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 ByteMaskedArray(Content):
def __init__(self, mask, content, valid_when):
assert isinstance(mask, list)
assert isinstance(content, Content)
assert isinstance(valid_when, bool)
for x in mask:
assert isinstance(x, bool)
assert len(mask) <= len(content)
self.mask = mask
self.content = content
self.valid_when = valid_when
@staticmethod
def random(minlen, choices):
mask = []
for i in range(random_length(minlen)):
mask.append(bool(random.randint(0, 1)))
content = random.choice(choices).random(len(mask), choices)
return ByteMaskedArray(mask, content, bool(random.randint(0, 1)))
def __len__(self):
return len(self.mask)
def __getitem__(self, where):
if isinstance(where, int):
assert 0 <= where < len(self)
if self.mask[where] == self.valid_when:
return self.content[where]
else:
return None
elif isinstance(where, slice) and where.step is None:
return ByteMaskedArray(self.mask[where.start:where.stop],
self.content[where.start:where.stop],
valid_when=self.valid_when)
elif isinstance(where, str):
return ByteMaskedArray(self.mask, self.content[where], valid_when=self.valid_when)
else:
raise AssertionError(where)
def __repr__(self):
return ("ByteMaskedArray(" + repr(self.mask) + ", " + repr(self.content)
+ ", " + repr(self.valid_when) + ")")
def xml(self, indent="", pre="", post=""):
out = indent + pre + "<ByteMaskedArray>\n"
out += indent + " <valid_when>" + repr(self.valid_when) + "<valid_when>\n"
out += indent + " <mask>" + " ".join(str(x) for x in self.mask) + "</mask>\n"
out += self.content.xml(indent + " ", "<content>", "</content>\n")
out += indent + "</ByteMaskedArray>\n"
return out
Here is an example:
ByteMaskedArray([True, True, False, False, True, False, False, True, True, True, True, True],
RawArray([5.7, 4.5, 8.3, 4.1, 5.1, 4.1, 0.3, 6.4, 5.5, 9.5, 7.1, 7.7, 4.0,
4.8, 4.4, 2.9, 1.4, 4.8, 7.3, 4.9, 6.0, 0.6, 11.2, 6.1, 4.7, 4.1,
4.4, 5.9, 7.6, 6.3, 5.5, 11.0, 9.2, 5.3, 0.1, 1.2, 4.5, 6.4, 2.8,
1.4, 5.8]),
False)
<ByteMaskedArray>
<valid_when>False</valid_when>
<mask>True True False False True False False True True True True True</mask>
<content><RawArray>
<ptr>5.7 4.5 8.3 4.1 5.1 4.1 0.3 6.4 5.5 9.5 7.1 7.7 4.0 4.8 4.4 2.9 1.4 4.8 7.3 4.9
6.0 0.6 11.2 6.1 4.7 4.1 4.4 5.9 7.6 6.3 5.5 11.0 9.2 5.3 0.1 1.2 4.5 6.4 2.8
1.4 5.8</ptr>
</RawArray></content>
</ByteMaskedArray>
which represents the following logical data.
[None, None, 8.3, 4.1, None, 4.1, 0.3, None, None, None, None, None]
In addition to the properties and methods described in ak.layout.Content, a ByteMaskedArray has the following.
ak.layout.ByteMaskedArray.__init__¶
- ak.layout.ByteMaskedArray.__init__(mask, content, valid_when, identities=None, parameters=None)¶
ak.layout.ByteMaskedArray.project¶
- ak.layout.ByteMaskedArray.project(mask=None)¶
Returns a non-ak.types.OptionType array containing only the valid elements.
If mask is a signed 8-bit ak.layout.Index in which 0 means valid
and 1 means missing, this mask is unioned with the ByteMaskedArray’s
mask (after converting to valid_when=False to match this mask).
ak.layout.ByteMaskedArray.bytemask¶
- ak.layout.ByteMaskedArray.bytemask()¶
Returns an array of 8-bit values in which 0 means valid and 1 means missing.
ak.layout.ByteMaskedArray.simplify¶
- ak.layout.ByteMaskedArray.simplify()¶
Combines this node with its content if the content also has
ak.types.OptionType; otherwise, this is a pass-through.
In all cases, the output has the same logical meaning as the input.
This method only operates one level deep.