Fixed #27235 -- Removed some usage of mutable default arguments.

django/db/backends/base/schema.py

@@ -94,7 +94,7 @@ class BaseDatabaseSchemaEditor(object):
 
     # Core utility functions
 
-    def execute(self, sql, params=[]):
+    def execute(self, sql, params=()):
         """
         Executes the given SQL statement, with optional parameters.
         """

django/db/models/fields/__init__.py

@@ -142,7 +142,7 @@ class Field(RegisterLookupMixin):
                  db_index=False, rel=None, default=NOT_PROVIDED, editable=True,
                  serialize=True, unique_for_date=None, unique_for_month=None,
                  unique_for_year=None, choices=None, help_text='', db_column=None,
-                 db_tablespace=None, auto_created=False, validators=[],
+                 db_tablespace=None, auto_created=False, validators=(),
                  error_messages=None):
         self.name = name
         self.verbose_name = verbose_name  # May be set by set_attributes_from_name
@@ -175,7 +175,7 @@ class Field(RegisterLookupMixin):
             self.creation_counter = Field.creation_counter
             Field.creation_counter += 1
 
-        self._validators = validators  # Store for deconstruction later
+        self._validators = list(validators)  # Store for deconstruction later
 
         messages = {}
         for c in reversed(self.__class__.__mro__):

django/forms/fields.py

@@ -62,7 +62,7 @@ class Field(object):
 
     def __init__(self, required=True, widget=None, label=None, initial=None,
                  help_text='', error_messages=None, show_hidden_initial=False,
-                 validators=[], localize=False, disabled=False, label_suffix=None):
+                 validators=(), localize=False, disabled=False, label_suffix=None):
         # required -- Boolean that specifies whether the field is required.
         #             True by default.
         # widget -- A Widget class, or instance of a Widget class, that should