pylint/checkers/base.py
def visit_lambda(self, node):
        """check whether or not the lambda is suspicious
        """
        # if the body of the lambda is a call expression with the same
        # argument list as the lambda itself, then the lambda is
        # possibly unnecessary and at least suspicious.
        if node.args.defaults:
            # If the arguments of the lambda include defaults, then a
            # judgment cannot be made because there is no way to check
            # that the defaults defined by the lambda are the same as
            # the defaults defined by the function called in the body
            # of the lambda.
            return
        call = node.body
        if not isinstance(call, astroid.Call):
            # The body of the lambda must be a function call expression
            # for the lambda to be unnecessary.
            return
        if isinstance(node.body.func, astroid.Attribute) and isinstance(
            node.body.func.expr, astroid.Call
        ):
            # Chained call, the intermediate call might
            # return something else (but we don't check that, yet).
            return

        call_site = CallSite.from_call(call)
        ordinary_args = list(node.args.args)
        new_call_args = list(self._filter_vararg(node, call.args))
        if node.args.kwarg:
            if self._has_variadic_argument(call.kwargs, node.args.kwarg):
                return

        if node.args.vararg:
            if self._has_variadic_argument(call.starargs, node.args.vararg):
                return
        elif call.starargs:
            return

        if call.keywords:
            # Look for additional keyword arguments that are not part
            # of the lambda's signature
            lambda_kwargs = {keyword.name for keyword in node.args.defaults}
            if len(lambda_kwargs) != len(call_site.keyword_arguments):
                # Different lengths, so probably not identical
                return
            if set(call_site.keyword_arguments).difference(lambda_kwargs):
                return

        # The "ordinary" arguments must be in a correspondence such that:
        # ordinary_args[i].name == call.args[i].name.
        if len(ordinary_args) != len(new_call_args):
            return
        for arg, passed_arg in zip(ordinary_args, new_call_args):
            if not isinstance(passed_arg, astroid.Name):
                return
            if arg.name != passed_arg.name:
                return

        self.add_message("unnecessary-lambda", line=node.fromlineno, node=node)
def visit_lambda(self, node):
        """check whether or not the lambda is suspicious
        """
        # if the body of the lambda is a call expression with the same
        # argument list as the lambda itself, then the lambda is
        # possibly unnecessary and at least suspicious.
        if node.args.defaults:
            # If the arguments of the lambda include defaults, then a
            # judgment cannot be made because there is no way to check
            # that the defaults defined by the lambda are the same as
            # the defaults defined by the function called in the body
            # of the lambda.
            return
        call = node.body
        if not isinstance(call, astroid.Call):
            # The body of the lambda must be a function call expression
            # for the lambda to be unnecessary.
            return
        if isinstance(node.body.func, astroid.Attribute) and isinstance(
            node.body.func.expr, astroid.Call
        ):
            # Chained call, the intermediate call might
            # return something else (but we don't check that, yet).
            return

        call_site = CallSite.from_call(call)
        ordinary_args = list(node.args.args)
        new_call_args = list(self._filter_vararg(node, call.args))
        if node.args.kwarg:
            if self._has_variadic_argument(call.kwargs, node.args.kwarg):
                return

        if node.args.vararg:
            if self._has_variadic_argument(call.starargs, node.args.vararg):
                return
        elif call.starargs:
            return

        if call.keywords:
            # Look for additional keyword arguments that are not part
            # of the lambda's signature
            lambda_kwargs = {keyword.name for keyword in node.args.defaults}
            if len(lambda_kwargs) != len(call_site.keyword_arguments):
                # Different lengths, so probably not identical
                return
            if set(call_site.keyword_arguments).difference(lambda_kwargs):
                return

        # The "ordinary" arguments must be in a correspondence such that:
        # ordinary_args[i].name == call.args[i].name.
        if len(ordinary_args) != len(new_call_args):
            return
        for arg, passed_arg in zip(ordinary_args, new_call_args):
            if not isinstance(passed_arg, astroid.Name):
                return
            if arg.name != passed_arg.name:
                return

        self.add_message("unnecessary-lambda", line=node.fromlineno, node=node)
check whether or not the lambda is suspicious