Avoid mutable default arguments (#342)

While they are not always an actual bug, they are certainly a Python
anti-pattern and possible the source of future bugs.

In at least one case, the default mutable argument `config` is actually
modified later on by the function.

Author: DimitriPapadopoulos

numpydoc/docscrape.py

@@ -136,7 +136,7 @@ class NumpyDocString(Mapping):
         'index': {}
     }
 
-    def __init__(self, docstring, config={}):
+    def __init__(self, docstring, config=None):
         orig_docstring = docstring
         docstring = textwrap.dedent(docstring).split('\n')
 
@@ -553,14 +553,16 @@ def dedent_lines(lines):
 
 
 class FunctionDoc(NumpyDocString):
-    def __init__(self, func, role='func', doc=None, config={}):
+    def __init__(self, func, role='func', doc=None, config=None):
         self._f = func
         self._role = role  # e.g. "func" or "meth"
 
         if doc is None:
             if func is None:
                 raise ValueError("No function or docstring given")
             doc = inspect.getdoc(func) or ''
+        if config is None:
+            config = {}
         NumpyDocString.__init__(self, doc, config)
 
     def get_func(self):
@@ -590,8 +592,10 @@ def __str__(self):
 
 
 class ObjDoc(NumpyDocString):
-    def __init__(self, obj, doc=None, config={}):
+    def __init__(self, obj, doc=None, config=None):
         self._f = obj
+        if config is None:
+            config = {}
         NumpyDocString.__init__(self, doc, config=config)
 
 
@@ -600,7 +604,7 @@ class ClassDoc(NumpyDocString):
     extra_public_methods = ['__call__']
 
     def __init__(self, cls, doc=None, modulename='', func_doc=FunctionDoc,
-                 config={}):
+                 config=None):
         if not inspect.isclass(cls) and cls is not None:
             raise ValueError("Expected a class or None, but got %r" % cls)
         self._cls = cls
@@ -610,6 +614,8 @@ def __init__(self, cls, doc=None, modulename='', func_doc=FunctionDoc,
         else:
             ALL = object()
 
+        if config is None:
+            config = {}
         self.show_inherited_members = config.get(
                     'show_inherited_class_members', True)
 
@@ -679,7 +685,7 @@ def _is_show_member(self, name):
         return True
 
 
-def get_doc_object(obj, what=None, doc=None, config={}):
+def get_doc_object(obj, what=None, doc=None, config=None):
     if what is None:
         if inspect.isclass(obj):
             what = 'class'
@@ -689,6 +695,8 @@ def get_doc_object(obj, what=None, doc=None, config={}):
             what = 'function'
         else:
             what = 'object'
+    if config is None:
+        config = {}
 
     if what == 'class':
         return ClassDoc(obj, func_doc=FunctionDoc, doc=doc, config=config)

numpydoc/docscrape_sphinx.py

@@ -18,7 +18,9 @@
 
 
 class SphinxDocString(NumpyDocString):
-    def __init__(self, docstring, config={}):
+    def __init__(self, docstring, config=None):
+        if config is None:
+            config = {}
         NumpyDocString.__init__(self, docstring, config=config)
         self.load_config(config)
 
@@ -392,25 +394,31 @@ def __str__(self, indent=0, func_role="obj"):
 
 
 class SphinxFunctionDoc(SphinxDocString, FunctionDoc):
-    def __init__(self, obj, doc=None, config={}):
+    def __init__(self, obj, doc=None, config=None):
+        if config is None:
+            config = {}
         self.load_config(config)
         FunctionDoc.__init__(self, obj, doc=doc, config=config)
 
 
 class SphinxClassDoc(SphinxDocString, ClassDoc):
-    def __init__(self, obj, doc=None, func_doc=None, config={}):
+    def __init__(self, obj, doc=None, func_doc=None, config=None):
+        if config is None:
+            config = {}
         self.load_config(config)
         ClassDoc.__init__(self, obj, doc=doc, func_doc=None, config=config)
 
 
 class SphinxObjDoc(SphinxDocString, ObjDoc):
-    def __init__(self, obj, doc=None, config={}):
+    def __init__(self, obj, doc=None, config=None):
+        if config is None:
+            config = {}
         self.load_config(config)
         ObjDoc.__init__(self, obj, doc=doc, config=config)
 
 
 # TODO: refactor to use docscrape.get_doc_object
-def get_doc_object(obj, what=None, doc=None, config={}, builder=None):
+def get_doc_object(obj, what=None, doc=None, config=None, builder=None):
     if what is None:
         if inspect.isclass(obj):
             what = 'class'
@@ -421,6 +429,8 @@ def get_doc_object(obj, what=None, doc=None, config={}, builder=None):
         else:
             what = 'object'
 
+    if config is None:
+        config = {}
     template_dirs = [os.path.join(os.path.dirname(__file__), 'templates')]
     if builder is not None:
         template_loader = BuiltinTemplateLoader()

numpydoc/tests/test_docscrape.py

@@ -225,7 +225,7 @@ def test_returns(doc):
     assert arg_type == 'ndarray'
     assert desc[0].startswith('The drawn samples')
     assert desc[-1].endswith('distribution.')
-    
+
     arg, arg_type, desc = doc['Returns'][1]
     assert arg == ''
     assert arg_type == 'list of str'

numpydoc/xref.py

@@ -108,7 +108,7 @@ def make_xref(param_type, xref_aliases, xref_ignore):
         to fully qualified names that can be cross-referenced.
     xref_ignore : set or "all"
         A set containing words not to cross-reference. Instead of a set, the
-        string 'all' can be given to ignore all unrecognized terms. 
+        string 'all' can be given to ignore all unrecognized terms.
         Unrecognized terms include those that are not in `xref_aliases` and
         are not already wrapped in a reST role.