Instance vs class vs static method

All three are defined in a class, but they receive different implicit arguments.

| Kind | Decorator | First arg | Typical use | | --- | --- | --- | --- | | Instance method | (none) | self (instance) | Read/write instance state | | Class method | @classmethod | cls (class) | Alternative constructors, class-wide config | | Static method | @staticmethod | none | Namespaced utility related to the class |

class Job:
    default_queue = "default"

    def __init__(self, name, queue=None):
        self.name = name
        self.queue = queue or self.default_queue

    def summary(self):                 # instance
        return f"{self.name}@{self.queue}"

    @classmethod
    def from_dict(cls, data):          # class
        return cls(data["name"], data.get("queue"))

    @staticmethod
    def valid_name(name: str) -> bool: # static
        return bool(name and name.strip())

job = Job.from_dict({"name": "etl"})
print(job.summary())
print(Job.valid_name("etl"))

Rule of thumb: Need instance data → instance method. Need to construct/customize by class → classmethod. No self/cls needed but it still belongs with the class → staticmethod (or a module-level function).