from ....common.graft import client
from ...cereal import serializable
from ..core import Proxytype, typecheck_promote, merge_params
from ..primitives import Int, NoneType
[docs]@serializable()
class Slice(Proxytype):
"""
Proxy Slice object.
Internal class used as a promotion target for Python slices.
You shouldn't use this directly; Python slices can be used to achieve the same result.
Examples
--------
>>> from descarteslabs.workflows import List, Int
>>> from descarteslabs.workflows.types.containers import Slice
>>> my_slice = Slice(0, 4, 2)
>>> my_slice
<descarteslabs.workflows.types.containers.slice.Slice object at 0x...>
>>> my_slice.compute() # doctest: +SKIP
slice(0, 4, 2)
>>> my_list = List[Int]([1, 2, 3, 4, 5])
>>> my_list[my_slice].compute() # doctest: +SKIP
[1, 3]
"""
@typecheck_promote(
start=(Int, NoneType), stop=(Int, NoneType), step=(Int, NoneType)
)
def __init__(self, start=None, stop=None, step=None):
if not (
(isinstance(start, Int) and start.literal_value is None)
or (isinstance(stop, Int) and stop.literal_value is None)
or (isinstance(step, Int) and step.literal_value is None)
):
self._literal_value = slice(
start.literal_value, stop.literal_value, step.literal_value
)
self.graft = client.apply_graft(
"wf.Slice.create", start=start, stop=stop, step=step
)
self.params = merge_params(start, stop, step)
[docs] @classmethod
def from_slice(cls, obj):
"""Construct a Workflows Slice from a Python slice object.
Example
-------
>>> from descarteslabs.workflows.types.containers import Slice
>>> py_slice = slice(0, 4, 2)
>>> my_slice = Slice.from_slice(py_slice)
>>> my_slice.compute() # doctest: +SKIP
slice(0, 4, 2)
"""
return cls(start=obj.start, stop=obj.stop, step=obj.step)
@classmethod
def _promote(cls, obj):
if isinstance(obj, cls):
return obj
elif isinstance(obj, slice):
return cls.from_slice(obj)
else:
return super(Slice, cls)._promote(obj)
@property
def literal_value(self):
"Python literal value this proxy object was constructed with, or None if not constructed from a literal value."
return getattr(self, "_literal_value", None)
