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dunder_methods.py
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dunder_methods.py
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# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
# For details: https://github.com/PyCQA/pylint/blob/main/LICENSE
# Copyright (c) https://github.com/PyCQA/pylint/blob/main/CONTRIBUTORS.txt
from __future__ import annotations
from typing import TYPE_CHECKING
from astroid import Instance, Uninferable, nodes
from pylint.checkers import BaseChecker
from pylint.checkers.utils import safe_infer
from pylint.interfaces import HIGH
if TYPE_CHECKING:
from pylint.lint import PyLinter
DUNDER_METHODS: dict[tuple[int, int], dict[str, str]] = {
(0, 0): {
"__init__": "Instantiate class directly",
"__del__": "Use del keyword",
"__repr__": "Use repr built-in function",
"__str__": "Use str built-in function",
"__bytes__": "Use bytes built-in function",
"__format__": "Use format built-in function, format string method, or f-string",
"__lt__": "Use < operator",
"__le__": "Use <= operator",
"__eq__": "Use == operator",
"__ne__": "Use != operator",
"__gt__": "Use > operator",
"__ge__": "Use >= operator",
"__hash__": "Use hash built-in function",
"__bool__": "Use bool built-in function",
"__getattr__": "Access attribute directly or use getattr built-in function",
"__getattribute__": "Access attribute directly or use getattr built-in function",
"__setattr__": "Set attribute directly or use setattr built-in function",
"__delattr__": "Use del keyword",
"__dir__": "Use dir built-in function",
"__get__": "Use get method",
"__set__": "Use set method",
"__delete__": "Use del keyword",
"__instancecheck__": "Use isinstance built-in function",
"__subclasscheck__": "Use issubclass built-in function",
"__call__": "Invoke instance directly",
"__len__": "Use len built-in function",
"__length_hint__": "Use length_hint method",
"__getitem__": "Access item via subscript",
"__setitem__": "Set item via subscript",
"__delitem__": "Use del keyword",
"__iter__": "Use iter built-in function",
"__next__": "Use next built-in function",
"__reversed__": "Use reversed built-in function",
"__contains__": "Use in keyword",
"__add__": "Use + operator",
"__sub__": "Use - operator",
"__mul__": "Use * operator",
"__matmul__": "Use @ operator",
"__truediv__": "Use / operator",
"__floordiv__": "Use // operator",
"__mod__": "Use % operator",
"__divmod__": "Use divmod built-in function",
"__pow__": "Use ** operator or pow built-in function",
"__lshift__": "Use << operator",
"__rshift__": "Use >> operator",
"__and__": "Use & operator",
"__xor__": "Use ^ operator",
"__or__": "Use | operator",
"__radd__": "Use + operator",
"__rsub__": "Use - operator",
"__rmul__": "Use * operator",
"__rmatmul__": "Use @ operator",
"__rtruediv__": "Use / operator",
"__rfloordiv__": "Use // operator",
"__rmod__": "Use % operator",
"__rdivmod__": "Use divmod built-in function",
"__rpow__": "Use ** operator or pow built-in function",
"__rlshift__": "Use << operator",
"__rrshift__": "Use >> operator",
"__rand__": "Use & operator",
"__rxor__": "Use ^ operator",
"__ror__": "Use | operator",
"__iadd__": "Use += operator",
"__isub__": "Use -= operator",
"__imul__": "Use *= operator",
"__imatmul__": "Use @= operator",
"__itruediv__": "Use /= operator",
"__ifloordiv__": "Use //= operator",
"__imod__": "Use %= operator",
"__ipow__": "Use **= operator",
"__ilshift__": "Use <<= operator",
"__irshift__": "Use >>= operator",
"__iand__": "Use &= operator",
"__ixor__": "Use ^= operator",
"__ior__": "Use |= operator",
"__neg__": "Multiply by -1 instead",
"__pos__": "Multiply by +1 instead",
"__abs__": "Use abs built-in function",
"__invert__": "Use ~ operator",
"__complex__": "Use complex built-in function",
"__int__": "Use int built-in function",
"__float__": "Use float built-in function",
"__index__": "Use index method",
"__round__": "Use round built-in function",
"__trunc__": "Use math.trunc function",
"__floor__": "Use math.floor function",
"__ceil__": "Use math.ceil function",
"__enter__": "Invoke context manager directly",
"__aenter__": "Invoke context manager directly",
"__copy__": "Use copy.copy function",
"__deepcopy__": "Use copy.deepcopy function",
"__fspath__": "Use os.fspath function instead",
},
(3, 10): {
"__aiter__": "Use aiter built-in function",
"__anext__": "Use anext built-in function",
},
}
class DunderCallChecker(BaseChecker):
"""Check for unnecessary dunder method calls.
Docs: https://docs.python.org/3/reference/datamodel.html#basic-customization
We exclude __new__, __subclasses__, __init_subclass__, __set_name__,
__class_getitem__, __missing__, __exit__, __await__,
__aexit__, __getnewargs_ex__, __getnewargs__, __getstate__,
__setstate__, __reduce__, __reduce_ex__
since these either have no alternative method of being called or
have a genuine use case for being called manually.
Additionally, we exclude classes that are not instantiated since these
might be used to access the dunder methods of a base class of an instance.
We also exclude dunder method calls on super() since
these can't be written in an alternative manner.
"""
name = "unnecessary-dunder-call"
priority = -1
msgs = {
"C2801": (
"Unnecessarily calls dunder method %s. %s.",
"unnecessary-dunder-call",
"Used when a dunder method is manually called instead "
"of using the corresponding function/method/operator.",
),
}
options = ()
def open(self) -> None:
self._dunder_methods: dict[str, str] = {}
for since_vers, dunder_methods in DUNDER_METHODS.items():
if since_vers <= self.linter.config.py_version:
self._dunder_methods.update(dunder_methods)
@staticmethod
def within_dunder_def(node: nodes.NodeNG) -> bool:
"""Check if dunder method call is within a dunder method definition."""
parent = node.parent
while parent is not None:
if (
isinstance(parent, nodes.FunctionDef)
and parent.name.startswith("__")
and parent.name.endswith("__")
):
return True
parent = parent.parent
return False
def visit_call(self, node: nodes.Call) -> None:
"""Check if method being called is an unnecessary dunder method."""
if (
isinstance(node.func, nodes.Attribute)
and node.func.attrname in self._dunder_methods
and not self.within_dunder_def(node)
and not (
isinstance(node.func.expr, nodes.Call)
and isinstance(node.func.expr.func, nodes.Name)
and node.func.expr.func.name == "super"
)
):
inf_expr = safe_infer(node.func.expr)
if not (inf_expr in {None, Uninferable} or isinstance(inf_expr, Instance)):
# Skip dunder calls to non instantiated classes.
return
self.add_message(
"unnecessary-dunder-call",
node=node,
args=(node.func.attrname, self._dunder_methods[node.func.attrname]),
confidence=HIGH,
)
def register(linter: PyLinter) -> None:
linter.register_checker(DunderCallChecker(linter))