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# -*- coding: utf-8 -*-
# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
# For details: https://github.com/PyCQA/pylint/blob/master/COPYING
import astroid
from pylint import checkers, interfaces
from pylint.checkers import utils
class RecommendationChecker(checkers.BaseChecker):
__implements__ = (interfaces.IAstroidChecker,)
name = "refactoring"
msgs = {
"C0200": (
"Consider using enumerate instead of iterating with range and len",
"consider-using-enumerate",
"Emitted when code that iterates with range and len is "
"encountered. Such code can be simplified by using the "
"enumerate builtin.",
),
"C0201": (
"Consider iterating the dictionary directly instead of calling .keys()",
"consider-iterating-dictionary",
"Emitted when the keys of a dictionary are iterated through the .keys() "
"method. It is enough to just iterate through the dictionary itself, as "
'in "for key in dictionary".',
),
}
@staticmethod
def _is_builtin(node, function):
inferred = utils.safe_infer(node)
if not inferred:
return False
return utils.is_builtin_object(inferred) and inferred.name == function
@utils.check_messages("consider-iterating-dictionary")
def visit_call(self, node):
if not isinstance(node.func, astroid.Attribute):
return
if node.func.attrname != "keys":
return
if not isinstance(node.parent, (astroid.For, astroid.Comprehension)):
return
inferred = utils.safe_infer(node.func)
if not isinstance(inferred, astroid.BoundMethod) or not isinstance(
inferred.bound, astroid.Dict
):
return
if isinstance(node.parent, (astroid.For, astroid.Comprehension)):
self.add_message("consider-iterating-dictionary", node=node)
@utils.check_messages("consider-using-enumerate")
def visit_for(self, node):
"""Emit a convention whenever range and len are used for indexing."""
# Verify that we have a `range([start], len(...), [stop])` call and
# that the object which is iterated is used as a subscript in the
# body of the for.
# Is it a proper range call?
if not isinstance(node.iter, astroid.Call):
return
if not self._is_builtin(node.iter.func, "range"):
return
is_constant_zero = (
isinstance(node.iter.args[0], astroid.Const)
and node.iter.args[0].value == 0
)
if len(node.iter.args) == 2 and not is_constant_zero:
return
if len(node.iter.args) > 2:
return
# Is it a proper len call?
if not isinstance(node.iter.args[-1], astroid.Call):
return
second_func = node.iter.args[-1].func
if not self._is_builtin(second_func, "len"):
return
len_args = node.iter.args[-1].args
if not len_args or len(len_args) != 1:
return
iterating_object = len_args[0]
if not isinstance(iterating_object, astroid.Name):
return
# If we're defining __iter__ on self, enumerate won't work
scope = node.scope()
if iterating_object.name == "self" and scope.name == "__iter__":
return
# Verify that the body of the for loop uses a subscript
# with the object that was iterated. This uses some heuristics
# in order to make sure that the same object is used in the
# for body.
for child in node.body:
for subscript in child.nodes_of_class(astroid.Subscript):
if not isinstance(subscript.value, astroid.Name):
continue
value = subscript.slice
if isinstance(value, astroid.Index):
value = value.value
if not isinstance(value, astroid.Name):
continue
if value.name != node.target.name:
continue
if iterating_object.name != subscript.value.name:
continue
if subscript.value.scope() != node.scope():
# Ignore this subscript if it's not in the same
# scope. This means that in the body of the for
# loop, another scope was created, where the same
# name for the iterating object was used.
continue
self.add_message("consider-using-enumerate", node=node)
return
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