Issue 488/remove mutable default args in panel (#694)

* remove dangerous_default_arg from param_reprs

* remove dangerous default value warning from Viewable.save

* fix dangerouse default value for stages in Pipeline constructor

* fix dangerous default for kwargs _InteractFactory constructor

* fix bug with stages var in pipeline constructor

* remove dangerous default for widget_types in HoloViews.widgets_from_dimensions

panel/interact.py

@@ -379,10 +379,10 @@ class _InteractFactory(object):
     kwargs: dict
       A dict of **kwargs to use for widgets.
     """
-    def __init__(self, cls, options, kwargs={}):
+    def __init__(self, cls, options, kwargs=None):
         self.cls = cls
         self.opts = options
-        self.kwargs = kwargs
+        self.kwargs = kwargs or {}
 
     def widget(self, f):
         """

panel/pane/holoviews.py

@@ -280,7 +280,7 @@ def applies(cls, obj):
         return isinstance(obj, Dimensioned) or isinstance(obj, Plot)
 
     @classmethod
-    def widgets_from_dimensions(cls, object, widget_types={}, widgets_type='individual'):
+    def widgets_from_dimensions(cls, object, widget_types=None, widgets_type='individual'):
         from holoviews.core import Dimension, DynamicMap
         from holoviews.core.options import SkipRendering
         from holoviews.core.util import isnumeric, unicode, datetime_types, unique_iterator
@@ -289,6 +289,9 @@ def widgets_from_dimensions(cls, object, widget_types={}, widgets_type='individu
         from holoviews.plotting.util import get_dynamic_mode
         from ..widgets import Widget, DiscreteSlider, Select, FloatSlider, DatetimeInput, IntSlider
 
+        if widget_types is None:
+            widget_types = {}
+
         if isinstance(object, GenericCompositePlot):
             object = object.layout
         elif isinstance(object, Plot):

panel/pipeline.py

@@ -29,13 +29,13 @@ class Pipeline(param.Parameterized):
 
     previous = param.Action(default=lambda x: x.param.trigger('previous'))
 
-    def __init__(self, stages=[], **params):
+    def __init__(self, stages=None, **params):
         try:
             import holoviews as hv
         except:
             raise ImportError('Pipeline requires holoviews to be installed')
 
-        self._stages = list(stages)
+        self._stages = [] if stages is None else list(stages)
         self._stage = 0
         super(Pipeline, self).__init__(**params)
         self._error = Markdown('')
@@ -50,7 +50,7 @@ def __init__(self, stages=[], **params):
         spinner = Pane(os.path.join(os.path.dirname(__file__), 'assets', 'spinner.gif'))
         self._spinner_layout = Row(HSpacer(), Column(VSpacer(), spinner, VSpacer()), HSpacer())
         stage_layout = Row()
-        if len(stages):
+        if stages:
             stage_layout.append(self._init_stage())
         self._layout = Column(self._progress_bar, self._error, stage_layout)
 

panel/util.py

@@ -118,7 +118,7 @@ def abbreviated_repr(value, max_length=25, natural_breaks=(',', ' ')):
     return vrepr
 
 
-def param_reprs(parameterized, skip=[]):
+def param_reprs(parameterized, skip=None):
     """
     Returns a list of reprs for parameters on the parameterized object.
     Skips default and empty values.
@@ -131,7 +131,7 @@ def param_reprs(parameterized, skip=[]):
         elif isinstance(v, string_types) and v == '': continue
         elif isinstance(v, list) and v == []: continue
         elif isinstance(v, dict) and v == {}: continue
-        elif p in skip or (p == 'name' and v.startswith(cls)): continue
+        elif (skip and p in skip) or (p == 'name' and v.startswith(cls)): continue
         param_reprs.append('%s=%s' % (p, abbreviated_repr(v)))
     return param_reprs
 

panel/viewable.py

@@ -422,7 +422,7 @@ def get_root(self, doc=None, comm=None):
         return root
 
     def save(self, filename, title=None, resources=None, template=None,
-             template_variables={}, embed=False, max_states=1000,
+             template_variables=None, embed=False, max_states=1000,
              max_opts=3, embed_json=False, json_prefix='', save_path='./',
              load_path=None):
         """
@@ -436,6 +436,10 @@ def save(self, filename, title=None, resources=None, template=None,
            Optional title for the plot
         resources: bokeh resources
            One of the valid bokeh.resources (e.g. CDN or INLINE)
+       template:
+           passed to underlying io.save
+       template_variables:
+           passed to underlying io.save
         embed: bool
            Whether the state space should be embedded in the saved file.
         max_states: int