Source code for holoviews.core.operation

"""
Operations manipulate Elements, HoloMaps and Layouts, typically for
the purposes of analysis or visualization.
"""
from functools import reduce
import param

try:
    from itertools import izip as zip
except:
    pass

from .dimension import ViewableElement
from .element import Element, HoloMap, GridSpace, Collator
from .layout import Layout
from .overlay import NdOverlay, Overlay
from .spaces import DynamicMap, Callable
from .traversal import unique_dimkeys
from . import util


[docs]class Operation(param.ParameterizedFunction): """ Base class for all Operation types. """ group = param.String(default='Operation', doc=""" The group string used to identify the output of the Operation. By default this should match the operation name.""") @classmethod
[docs] def search(cls, element, pattern): """ Helper method that returns a list of elements that match the given path pattern of form {type}.{group}.{label}. The input may be a Layout, an Overlay type or a single Element. """ if isinstance(element, Layout): return [el for cell in element for el in cls.search(cell, pattern)] if isinstance(element, (NdOverlay, Overlay)): return [el for el in element if el.matches(pattern)] elif isinstance(element, Element): return [element] if element.matches(pattern) else []
@classmethod
[docs] def get_overlay_label(cls, overlay, default_label=''): """ Returns a label if all the elements of an overlay agree on a consistent label, otherwise returns the default label. """ if all(el.label==overlay.get(0).label for el in overlay): return overlay.get(0).label else: return default_label
@classmethod
[docs] def get_overlay_bounds(cls, overlay): """ Returns the extents if all the elements of an overlay agree on a consistent extents, otherwise raises an exception. """ if all(el.bounds==overlay.get(0).bounds for el in overlay): return overlay.get(0).bounds else: raise ValueError("Extents across the overlay are inconsistent")
[docs]class ElementOperation(Operation): """ An ElementOperation process an Element or HoloMap at the level of individual elements or overlays. If a holomap is passed in as input, a processed holomap is returned as output where the individual elements have been transformed accordingly. An ElementOperation may turn overlays in new elements or vice versa. An ElementOperation can be set to be dynamic, which will return a DynamicMap with a callback that will apply the operation dynamically. An ElementOperation may also supply a list of Stream classes on a streams parameter, which can allow dynamic control over the parameters on the operation. """ dynamic = param.ObjectSelector(default='default', objects=['default', True, False], doc=""" Whether the operation should be applied dynamically when a specific frame is requested, specified as a Boolean. If set to 'default' the mode will be determined based on the input type, i.e. if the data is a DynamicMap it will stay dynamic.""") input_ranges = param.ClassSelector(default={}, class_=(dict, tuple), doc=""" Ranges to be used for input normalization (if applicable) in a format appropriate for the Normalization.ranges parameter. By default, no normalization is applied. If key-wise normalization is required, a 2-tuple may be supplied where the first component is a Normalization.ranges list and the second component is Normalization.keys. """) def _process(self, view, key=None): """ Process a single input element and outputs new single element or overlay. If a HoloMap is passed into a ElementOperation, the individual components are processed sequentially with the corresponding key passed as the optional key argument. """ raise NotImplementedError
[docs] def process_element(self, element, key, **params): """ The process_element method allows a single element to be operated on given an externally supplied key. """ self.p = param.ParamOverrides(self, params) return self._process(element, key)
def __call__(self, element, **params): self.p = param.ParamOverrides(self, params) dynamic = ((self.p.dynamic == 'default' and isinstance(element, DynamicMap)) or self.p.dynamic is True) if isinstance(element, GridSpace): # Initialize an empty axis layout grid_data = ((pos, self(cell, **params)) for pos, cell in element.items()) processed = GridSpace(grid_data, label=element.label, kdims=element.kdims) elif dynamic: from ..util import Dynamic streams = getattr(self.p, 'streams', []) processed = Dynamic(element, streams=streams, operation=self, kwargs=params) elif isinstance(element, ViewableElement): processed = self._process(element) elif isinstance(element, DynamicMap): if any((not d.values) for d in element.kdims): raise ValueError('Applying a non-dynamic operation requires ' 'all DynamicMap key dimensions to define ' 'the sampling by specifying values.') samples = tuple(d.values for d in element.kdims) processed = self(element[samples], **params) elif isinstance(element, HoloMap): mapped_items = [(k, self._process(el, key=k)) for k, el in element.items()] refval = mapped_items[0][1] processed = element.clone(mapped_items, group=refval.group, label=refval.label) else: raise ValueError("Cannot process type %r" % type(element).__name__) return processed
[docs]class OperationCallable(Callable): """ OperationCallable allows wrapping an ElementOperation and the objects it is processing to allow traversing the operations applied on a DynamicMap. """ operation = param.ClassSelector(class_=ElementOperation, doc=""" The ElementOperation being wrapped.""")
[docs]class MapOperation(param.ParameterizedFunction): """ A MapOperation takes a HoloMap containing elements or overlays and processes them at the HoloMap level, returning arbitrary new HoloMap objects as output. Unlike ElementOperation, MapOperations can compute over all the keys and dimensions of the input map. """ group = param.String(default='MapOperation', doc=""" The group string to identify the output of the MapOperation. By default this will match the MapOperation name.""") def __call__(self, vmap, **params): self.p = param.ParamOverrides(self, params) if not isinstance(vmap, HoloMap): raise Exception('MapOperation can only process Maps.') return self._process(vmap) def _process(self, view): """ Process a single input HoloMap, returning a new HoloMap instance. """ raise NotImplementedError
[docs]class TreeOperation(Operation): """ A TreeOperation is the most general Operation type; it accepts any HoloViews datastructure and outputs a Layout containing one or more elements. """
[docs] def process_element(self, element, key, **params): """ The process_element method allows a single element to be operated on given an externally supplied key. """ self.p = param.ParamOverrides(self, params) maps = self._process(element, key) return reduce(lambda x,y: x + y, maps)
def __call__(self, src, **params): self.p = param.ParamOverrides(self, params) dims, keys = unique_dimkeys(src) if isinstance(src, Layout) and not src.uniform: raise Exception("TreeOperation can only process uniform Layouts") if not dims: return self.process_element(src, None) else: dim_names = [d.name for d in dims] values = {} for key in keys: selection = src.select(**dict(zip(dim_names, key))) if not isinstance(selection, Layout): selection = Layout.from_values([selection]) processed = self._process(selection, key) if isinstance(processed, list): processed = Layout.from_values(processed) values[key] = processed return Collator(values, kdims=dims)() def _process(self, tree, key=None): """ Process a single input Layout, returning a list of elements to be merged with the output Layout. """ raise NotImplementedError