Instance methods, i.e. methods not annotated with @classmethod or @staticmethod, are expected to have at least one
parameter. This parameter will reference the object instance on which the method is called. By convention, this first parameter is named "self".
Naming the "self" parameter differently is confusing. It might also indicate that the "self" parameter was forgotten, in which case calling the
method will most probably fail.
Note also that creating methods which are used as static methods without the @staticmethod decorator is a bad practice because calling
these methods on an instance will raise a TypeError. Either move the method out of the class or decorate it with
@staticmethod.
This rule raises an issue when the first parameter of an instance method is not called "self".
Noncompliant Code Example
class MyClass:
def send_request(request): # Noncompliant. "self" was probably forgotten
print("send_request")
class ClassWithStaticMethod:
def static_method(param): # Noncompliant
print(param)
ClassWithStaticMethod().static_method(42) # Method is available on the instance but calling it will raise a TypeError
Compliant Solution
class MyClass:
def send_request(self, request):
print("send_request")
class ClassWithStaticMethod:
@staticmethod
def static_method(param):
print(param)
ClassWithStaticMethod().static_method(42)
Exceptions
This rule will also accept "cls" or "mcs" as first parameter’s name for metaclasses' methods.
No issue will be raised for methods called __init_subclass__, __class_getitem__ or __new__ as these methods'
first parameter is a class.
You can also disable issues on methods decorated with a specific decorator. Add these decorators to this rule’s "ignoreDecorators" parameter.
With "ignoredDecorators" set to "abstractmethod"
from abc import abstractmethod, ABC
class MyClass(ABC):
@abstractmethod
def method(): # No issue, even if it is better in this case to also decorate with @staticmethod
pass
See
