11# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
22# For details: https://github.com/PyCQA/pylint/blob/master/LICENSE
3+ from typing import cast
34
45import astroid
56
@@ -26,6 +27,14 @@ class RecommendationChecker(checkers.BaseChecker):
2627 "method. It is enough to just iterate through the dictionary itself, as "
2728 'in "for key in dictionary".' ,
2829 ),
30+ "C0206" : (
31+ "Consider iterating with .items()" ,
32+ "consider-using-dict-items" ,
33+ "Emitted when iterating over the keys of a dictionary and accessing the "
34+ "value by index lookup."
35+ "Both the key and value can be accessed by iterating using the .items() "
36+ "method of the dictionary instead." ,
37+ ),
2938 }
3039
3140 @staticmethod
@@ -53,8 +62,12 @@ def visit_call(self, node):
5362 if isinstance (node .parent , (astroid .For , astroid .Comprehension )):
5463 self .add_message ("consider-iterating-dictionary" , node = node )
5564
56- @utils .check_messages ("consider-using-enumerate" )
57- def visit_for (self , node ):
65+ @utils .check_messages ("consider-using-enumerate" , "consider-using-dict-items" )
66+ def visit_for (self , node : astroid .For ) -> None :
67+ self ._check_consider_using_enumerate (node )
68+ self ._check_consider_using_dict_items (node )
69+
70+ def _check_consider_using_enumerate (self , node : astroid .For ) -> None :
5871 """Emit a convention whenever range and len are used for indexing."""
5972 # Verify that we have a `range([start], len(...), [stop])` call and
6073 # that the object which is iterated is used as a subscript in the
@@ -119,3 +132,81 @@ def visit_for(self, node):
119132 continue
120133 self .add_message ("consider-using-enumerate" , node = node )
121134 return
135+
136+ def _check_consider_using_dict_items (self , node : astroid .For ) -> None :
137+ """Add message when accessing dict values by index lookup."""
138+ # Verify that we have a .keys() call and
139+ # that the object which is iterated is used as a subscript in the
140+ # body of the for.
141+
142+ iterating_object_name = utils .get_iterating_dictionary_name (node )
143+ if iterating_object_name is None :
144+ return
145+
146+ # Verify that the body of the for loop uses a subscript
147+ # with the object that was iterated. This uses some heuristics
148+ # in order to make sure that the same object is used in the
149+ # for body.
150+ for child in node .body :
151+ for subscript in child .nodes_of_class (astroid .Subscript ):
152+ subscript = cast (astroid .Subscript , subscript )
153+
154+ if not isinstance (subscript .value , (astroid .Name , astroid .Attribute )):
155+ continue
156+
157+ value = subscript .slice
158+ if isinstance (value , astroid .Index ):
159+ value = value .value
160+ if (
161+ not isinstance (value , astroid .Name )
162+ or value .name != node .target .name
163+ or iterating_object_name != subscript .value .as_string ()
164+ ):
165+ continue
166+ last_definition_lineno = value .lookup (value .name )[1 ][- 1 ].lineno
167+ if last_definition_lineno > node .lineno :
168+ # Ignore this subscript if it has been redefined after
169+ # the for loop. This checks for the line number using .lookup()
170+ # to get the line number where the iterating object was last
171+ # defined and compare that to the for loop's line number
172+ continue
173+ if (
174+ isinstance (subscript .parent , astroid .Assign )
175+ and subscript in subscript .parent .targets
176+ or isinstance (subscript .parent , astroid .AugAssign )
177+ and subscript == subscript .parent .target
178+ ):
179+ # Ignore this subscript if it is the target of an assignment
180+ continue
181+
182+ self .add_message ("consider-using-dict-items" , node = node )
183+ return
184+
185+ @utils .check_messages ("consider-using-dict-items" )
186+ def visit_comprehension (self , node : astroid .Comprehension ) -> None :
187+ iterating_object_name = utils .get_iterating_dictionary_name (node )
188+ if iterating_object_name is None :
189+ return
190+
191+ children = list (node .parent .get_children ())
192+ if node .ifs :
193+ children .extend (node .ifs )
194+ for child in children :
195+ for subscript in child .nodes_of_class (astroid .Subscript ):
196+ subscript = cast (astroid .Subscript , subscript )
197+
198+ if not isinstance (subscript .value , (astroid .Name , astroid .Attribute )):
199+ continue
200+
201+ value = subscript .slice
202+ if isinstance (value , astroid .Index ):
203+ value = value .value
204+ if (
205+ not isinstance (value , astroid .Name )
206+ or value .name != node .target .name
207+ or iterating_object_name != subscript .value .as_string ()
208+ ):
209+ continue
210+
211+ self .add_message ("consider-using-dict-items" , node = node )
212+ return
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