Fixed #28909 -- Simplified code using tuple/list/set/dict unpacking.

django/forms/boundfield.py

@@ -153,7 +153,7 @@ class BoundField:
         if id_:
             id_for_label = widget.id_for_label(id_)
             if id_for_label:
-                attrs = dict(attrs or {}, **{'for': id_for_label})
+                attrs = {**(attrs or {}), 'for': id_for_label}
             if self.field.required and hasattr(self.form, 'required_css_class'):
                 attrs = attrs or {}
                 if 'class' in attrs:

django/forms/fields.py

@@ -4,7 +4,6 @@ Field classes.
 
 import copy
 import datetime
-import itertools
 import math
 import os
 import re
@@ -112,7 +111,7 @@ class Field:
         messages.update(error_messages or {})
         self.error_messages = messages
 
-        self.validators = list(itertools.chain(self.default_validators, validators))
+        self.validators = [*self.default_validators, *validators]
 
         super().__init__()
 

django/forms/models.py

@@ -564,9 +564,7 @@ class BaseModelFormSet(BaseFormSet):
                  queryset=None, *, initial=None, **kwargs):
         self.queryset = queryset
         self.initial_extra = initial
-        defaults = {'data': data, 'files': files, 'auto_id': auto_id, 'prefix': prefix}
-        defaults.update(kwargs)
-        super().__init__(**defaults)
+        super().__init__(**{'data': data, 'files': files, 'auto_id': auto_id, 'prefix': prefix, **kwargs})
 
     def initial_form_count(self):
         """Return the number of forms that are required in this FormSet."""

django/forms/widgets.py

@@ -241,10 +241,7 @@ class Widget(metaclass=MediaDefiningClass):
 
     def build_attrs(self, base_attrs, extra_attrs=None):
         """Build an attribute dictionary."""
-        attrs = base_attrs.copy()
-        if extra_attrs is not None:
-            attrs.update(extra_attrs)
-        return attrs
+        return {**base_attrs, **(extra_attrs or {})}
 
     def value_from_datadict(self, data, files, name):
         """