matplotlib · Mrngilles · Mar 17, 2015 · Mar 22, 2016 · tonysyu · Mar 19, 2015
diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -886,6 +886,8 @@ def validate_animation_writer_path(p):
 
 # a map from key -> value, converter
 defaultParams = {
+    'style': [[''], validate_stringlist],
+
     'backend':           ['Agg', validate_backend],  # agg is certainly
                                                       # present
     'backend_fallback':  [True, validate_bool],  # agg is certainly present

diff --git a/lib/matplotlib/style/__init__.py b/lib/matplotlib/style/__init__.py
@@ -1,3 +1,6 @@
 from __future__ import absolute_import
 
 from .core import use, context, available, library, reload_library
+from matplotlib import rcParams
+if rcParams['style']:
+    use(rcParams['style'])
diff --git a/lib/matplotlib/style/core.py b/lib/matplotlib/style/core.py
@@ -17,6 +17,7 @@
 """
 import os
 import re
+import sys
 import contextlib
 import warnings
 
@@ -33,7 +34,7 @@
 USER_LIBRARY_PATHS = [os.path.join(mpl._get_configdir(), 'stylelib')]
 STYLE_EXTENSION = 'mplstyle'
 STYLE_FILE_PATTERN = re.compile('([\S]+).%s$' % STYLE_EXTENSION)
-
+PARENT_STYLES = 'style'
 
 # A list of rcParams that should not be applied from styles
 STYLE_BLACKLIST = {
@@ -91,26 +92,91 @@ def use(style):
     """
     if cbook.is_string_like(style) or hasattr(style, 'keys'):
         # If name is a single str or dict, make it a single element list.
-        styles = [style]
-    else:
-        styles = style
-
-    for style in styles:
-        if not cbook.is_string_like(style):
-            _apply_style(style)
-        elif style == 'default':
-            _apply_style(rcParamsDefault, warn=False)
-        elif style in library:
-            _apply_style(library[style])
+        style = [style]
+    flattened_style = _flatten_style_dict({PARENT_STYLES: style})
+    _apply_style(flattened_style)
+
+
+def _expand_parent(parent_style):
+    if cbook.is_string_like(parent_style):
+        if parent_style == "default":
+            parent_style = rcParamsDefault
         else:
-            try:
-                rc = rc_params_from_file(style, use_default_template=False)
-                _apply_style(rc)
-            except IOError:
-                msg = ("'%s' not found in the style library and input is "
-                       "not a valid URL or path. See `style.available` for "
-                       "list of available styles.")
-                raise IOError(msg % style)
+            parent_style = get_style_dict(parent_style)
+    return parent_style
+
+
+def flatten_inheritance_dict(child_dict, parent_key,
+                             expand_parent=lambda x: x):
+    """Return a flattened version of dictionary that inherits from a parent.
+
+    Parameters
+    ----------
+    child_dict : dict
+        Dictionary with a special key that points to a dictionary of defaults,
+        or a value that can be expanded to a dictionary of defaults.
+    parent_key : str
+        The key that points to a list of parents.
+    expand_parent : callable(parent) -> dict
+        Function that returns a dictionary from the value corresponding to
+        `parent_key`. By default, this simply returns the value.
+    """
+    if parent_key not in child_dict:
+        return child_dict.copy()
+
+    parents = child_dict[parent_key]
+    if isinstance(parents, dict):
+        parents = [parents]
+    if not isinstance(parents, (list, tuple)):
+        msg = "Parent value must be list or tuple, but given {!r}"
+        raise ValueError(msg.format(parents))
+
+    # Expand any parents defined by `child_dict` into dictionaries.
+    parents = (expand_parent(p) for p in parents)
+
+    # Resolve any grand-parents defined by parents of `child_dict`
+    parents = [flatten_inheritance_dict(p, parent_key, expand_parent)
+               for p in parents]
+
+    # Child will override parent values in `dict.update` so put it last.
+    ordered_dicts = parents + [child_dict]
+
+    # Copy first dictionary and update with subsequent dictionaries.
+    output_dict = ordered_dicts[0].copy()
+    for d in ordered_dicts[1:]:
+        output_dict.update(d)
+
+    # Since the parent data been resolved, remove parent references.
+    del output_dict[parent_key]
+    return output_dict
+
+
+def _flatten_style_dict(style_dict):
+    return flatten_inheritance_dict(style_dict, PARENT_STYLES,
+                                    expand_parent=_expand_parent)
+
+
+def get_style_dict(style):
+    """Returns a dictionnary containing all the parameters from the
+    style file.
+
+    Parameters
+    ----------
+    style : str
+        style from the default library, the personal library or any
+        full path.
+    """
+    if style in library:
+        return library[style]
+    else:
+        try:
+            return rc_params_from_file(style,
+                                       use_default_template=False)
+        except IOError:
+            msg = ("'%s' not found in the style library and input is "
+                   "not a valid URL or path. See `style.available` for "
+                   "list of available styles.")
+            raise IOError(msg % style)
 
 
 @contextlib.contextmanager

diff --git a/lib/matplotlib/tests/test_style.py b/lib/matplotlib/tests/test_style.py
@@ -7,12 +7,16 @@
 from collections import OrderedDict
 from contextlib import contextmanager
 
-from nose.tools import assert_raises
+from nose import SkipTest
+from nose.tools import assert_raises, assert_equal
 from nose.plugins.attrib import attr
 
 import matplotlib as mpl
 from matplotlib import style
-from matplotlib.style.core import USER_LIBRARY_PATHS, STYLE_EXTENSION
+from matplotlib.style.core import (USER_LIBRARY_PATHS,
+                                   STYLE_EXTENSION,
+                                   BASE_LIBRARY_PATH,
+                                   flatten_inheritance_dict, get_style_dict)
 
 import six
 
@@ -24,7 +28,8 @@
 @contextmanager
 def temp_style(style_name, settings=None):
     """Context manager to create a style sheet in a temporary directory."""
-    settings = DUMMY_SETTINGS
+    if not settings:
+        settings = DUMMY_SETTINGS
     temp_file = '%s.%s' % (style_name, STYLE_EXTENSION)
 
     # Write style settings to file in the temp directory.
@@ -130,6 +135,148 @@ def test_context_with_badparam():
         assert mpl.rcParams[PARAM] == other_value
 
 
+def test_get_style_dict():
+    style_dict = get_style_dict('bmh')
+    assert(isinstance(style_dict, dict))
+
+
+def test_get_style_dict_from_lib():
+    style_dict = get_style_dict('bmh')
+    assert_equal(style_dict['lines.linewidth'], 2.0)
+
+
+def test_get_style_dict_from_file():
+    style_dict = get_style_dict(os.path.join(BASE_LIBRARY_PATH,
+                                             'bmh.mplstyle'))
+    assert_equal(style_dict['lines.linewidth'], 2.0)
+
+
+def test_parent_stylesheet():
+    parent_value = 'blue'
+    parent = {PARAM: parent_value}
+    child = {'style': parent}
+    with style.context(child):
+        assert_equal(mpl.rcParams[PARAM], parent_value)
+
+
+def test_parent_stylesheet_children_override():
+    parent_value = 'blue'
+    child_value = 'gray'
+    parent = {PARAM: parent_value}
+    child = {'style': parent, PARAM: child_value}
+    with style.context(child):
+        assert_equal(mpl.rcParams[PARAM], child_value)
+
+
+def test_grandparent_stylesheet():
+    grandparent_value = 'blue'
+    grandparent = {PARAM: grandparent_value}
+    parent = {'style': grandparent}
+    child = {'style': parent}
+    with style.context(child):
+        assert_equal(mpl.rcParams[PARAM], grandparent_value)
+
+
+def test_parent_stylesheet_from_string():
+    parent_param = 'lines.linewidth'
+    parent_value = 2.0
+    parent = {parent_param: parent_value}
+    child = {'style': ['parent']}
+    with temp_style('parent', settings=parent):
+        with style.context(child):
+            assert_equal(mpl.rcParams[parent_param], parent_value)
+
+
+def test_parent_stylesheet_brothers():
+    parent_param = PARAM
+    parent_value1 = 'blue'
+    parent_value2 = 'gray'
+    parent1 = {parent_param: parent_value1}
+    parent2 = {parent_param: parent_value2}
+    child = {'style': [parent1, parent2]}
+    with style.context(child):
+        assert_equal(mpl.rcParams[parent_param], parent_value2)
+
+
+# Dictionnary flattening function tests
+def test_empty_dict():
+    child = {}
+    flattened = flatten_inheritance_dict(child, 'parents')
+    assert_equal(flattened, child)
+
+
+def test_no_parent():
+    child = {'my-key': 'my-value'}
+    flattened = flatten_inheritance_dict(child, 'parents')
+    assert_equal(flattened, child)
+    # Verify that flatten_inheritance_dict always returns a copy.
+    assert(flattened is not child)
+
+
+def test_non_list_raises():
+    child = {'parents': 'parent-value'}
+    assert_raises(ValueError, flatten_inheritance_dict, child,
+                  'parents')
+
+
+def test_child_with_no_unique_values():
+    parent = {'a': 1}
+    child = {'parents': [parent]}
+    flattened = flatten_inheritance_dict(child, 'parents')
+    assert_equal(flattened, parent)
+
+
+def test_child_overrides_parent_value():
+    parent = {'a': 'old-value'}
+    child = {'parents': [parent], 'a': 'new-value'}
+    flattened = flatten_inheritance_dict(child, 'parents')
+    assert_equal(flattened, {'a': 'new-value'})
+
+
+def test_parents_with_distinct_values():
+    child = {'parents': [{'a': 1}, {'b': 2}]}
+    flattened = flatten_inheritance_dict(child, 'parents')
+    assert_equal(flattened, {'a': 1, 'b': 2})
+
+
+def test_later_parent_overrides_former():
+    child = {'parents': [{'a': 1}, {'a': 2}]}
+    flattened = flatten_inheritance_dict(child, 'parents')
+    assert_equal(flattened, {'a': 2})
+
+
+def test_grandparent():
+    grandparent = {'a': 1}
+    parent = {'parents': [grandparent]}
+    child = {'parents': [parent]}
+    flattened = flatten_inheritance_dict(child, 'parents')
+    assert_equal(flattened, grandparent)
+
+
+def test_custom_expand_parent():
+    parent_map = {'a-pointer': {'a': 1}, 'b-pointer': {'b': 2}}
+
+    def expand_parent(key):
+        return parent_map[key]
+
+    child = {'parents': ['a-pointer', 'b-pointer']}
+    flattened = flatten_inheritance_dict(child, 'parents',
+                                         expand_parent=expand_parent)
+    assert_equal(flattened, {'a': 1, 'b': 2})
+
+
+def test_circular_parents():
+    parent_map = {'a-pointer': {'parents': ['b-pointer']},
+                  'b-pointer': {'parents': ['a-pointer']}}
+
+    def expand_parent(key):
+        return parent_map[key]
+
+    child = {'parents': ['a-pointer']}
+    assert_raises(RuntimeError, flatten_inheritance_dict, child,
+                 'parents', expand_parent=expand_parent)
+
+
 if __name__ == '__main__':
     from numpy import testing
     testing.run_module_suite()