Uploaded Test files

venv/Lib/site-packages/ipywidgets/widgets/widget_link.py

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+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+
+"""Link and DirectionalLink classes.
+
+Propagate changes between widgets on the javascript side.
+"""
+
+from .widget import Widget, register, widget_serialization
+from .widget_core import CoreWidget
+
+from traitlets import Unicode, Tuple, Instance, TraitError
+
+
+class WidgetTraitTuple(Tuple):
+    """Traitlet for validating a single (Widget, 'trait_name') pair"""
+
+    info_text = "A (Widget, 'trait_name') pair"
+
+    def __init__(self, **kwargs):
+        super(WidgetTraitTuple, self).__init__(Instance(Widget), Unicode(), **kwargs)
+
+    def validate_elements(self, obj, value):
+        value = super(WidgetTraitTuple, self).validate_elements(obj, value)
+        widget, trait_name = value
+        trait = widget.traits().get(trait_name)
+        trait_repr = "%s.%s" % (widget.__class__.__name__, trait_name)
+        # Can't raise TraitError because the parent will swallow the message
+        # and throw it away in a new, less informative TraitError
+        if trait is None:
+            raise TypeError("No such trait: %s" % trait_repr)
+        elif not trait.metadata.get('sync'):
+            raise TypeError("%s cannot be synced" % trait_repr)
+        return value
+
+
+@register
+class Link(CoreWidget):
+    """Link Widget
+
+    source: a (Widget, 'trait_name') tuple for the source trait
+    target: a (Widget, 'trait_name') tuple that should be updated
+    """
+
+    _model_name = Unicode('LinkModel').tag(sync=True)
+    target = WidgetTraitTuple(help="The target (widget, 'trait_name') pair").tag(sync=True, **widget_serialization)
+    source = WidgetTraitTuple(help="The source (widget, 'trait_name') pair").tag(sync=True, **widget_serialization)
+
+    def __init__(self, source, target, **kwargs):
+        kwargs['source'] = source
+        kwargs['target'] = target
+        super(Link, self).__init__(**kwargs)
+
+    # for compatibility with traitlet links
+    def unlink(self):
+        self.close()
+
+
+def jslink(attr1, attr2):
+    """Link two widget attributes on the frontend so they remain in sync.
+
+    The link is created in the front-end and does not rely on a roundtrip
+    to the backend.
+
+    Parameters
+    ----------
+    source : a (Widget, 'trait_name') tuple for the first trait
+    target : a (Widget, 'trait_name') tuple for the second trait
+
+    Examples
+    --------
+
+    >>> c = link((widget1, 'value'), (widget2, 'value'))
+    """
+    return Link(attr1, attr2)
+
+
+@register
+class DirectionalLink(Link):
+    """A directional link
+
+    source: a (Widget, 'trait_name') tuple for the source trait
+    target: a (Widget, 'trait_name') tuple that should be updated
+    when the source trait changes.
+    """
+    _model_name = Unicode('DirectionalLinkModel').tag(sync=True)
+
+
+def jsdlink(source, target):
+    """Link a source widget attribute with a target widget attribute.
+
+    The link is created in the front-end and does not rely on a roundtrip
+    to the backend.
+
+    Parameters
+    ----------
+    source : a (Widget, 'trait_name') tuple for the source trait
+    target : a (Widget, 'trait_name') tuple for the target trait
+
+    Examples
+    --------
+
+    >>> c = dlink((src_widget, 'value'), (tgt_widget, 'value'))
+    """
+    return DirectionalLink(source, target)