ensure classes have an init method

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Metadata

ID: python-best-practices/init-method-required

Language: Python

Severity: Notice

Category: Best Practices

Description

Ensure that a class has an __init__ method. This check is bypassed for dataclass-like decorators (@dataclass, @frozen, @bindable_dataclass).

Non-Compliant Code Examples

class Foo:  # need to define __init__
	def foo(bar):
		pass
	def bar(baz):
		pass

Compliant Code Examples

@define
class Foo:
	def foo(bar):
		pass
	def bar(baz):
		pass

import pandas as pd


@binding.bindable_dataclass
class MyClass:
    cost_source_type: str = "Metric"
    cost_metric_name: str = "test.evp.costs"
    cost_filter: str = ""
    datacenters: list[str] = field(default_factory=lambda: ["us1.prod.dog"])

    def fetch_something(self) -> pd.DataFrame:
        pass

# dataclass do not require an init class
@dataclass
class Requests:
    cpu: float  # expressed in cpu cores
    memory: int  # expressed in bytes

    @staticmethod
    def from_pod(pod: V1Pod):
        cpu = 0.0
        memory = 0

        for container in pod.spec.containers:
            cpu += parse_cpu_string(container.resources.requests["cpu"])
            memory += parse_memory_string(container.resources.requests["memory"])

        return Requests(cpu, memory)

    def add(self, other):
        self.cpu += other.cpu
        self.memory += other.memory

@dataclasses.dataclass
class DependencyKey:
    name: str
    version: str

    def __hash__(self):
        if self.version is None:
            version = ""
        else:
            version = self.version
        return hash(self.name + version)

@frozen
class AnotherClass:
    cpu: float
    memory: int
    def add(self, other):
        self.cpu += other.cpu
        self.memory += other.memory

@dataclasses.dataclass(frozen=True)
class Settings:
    keys: list[[str, str]]

    def get_keys(self):
        return self.keys

class Child(Parent):
  def fn():
      pass

class AnotherChild(modname.Parent):
  def another_fn():
    pass

class UserLoginTest(TestCase):
    def setUp(self):
        self.username = 'testuser'
        self.password = 'testpassword'
        self.user = User.objects.create_user(username=self.username, password=self.password)

    def test_correct_credentials(self):
        user = authenticate(username=self.username, password=self.password)
        self.assertIsNotNone(user)
        self.assertEqual(user, self.user)

    def test_incorrect_credentials(self):
        user = authenticate(username=self.username, password='wrongpassword')
        self.assertIsNone(user)

from django.db import migrations, models
import django.db.models.deletion


class Migration(migrations.Migration):

    dependencies = [
    ]

    operations = [
    ]

@dataclass
class Foo:  # no __init__ required for dataclass
	value = 51

class Foo:
	def __init__(self):
		pass