How to Avoid Circular Imports When Classes Depend on Each Other?

Avoiding Circular Imports in Python

In Python, circular imports can arise when two or more classes or modules depend on each other, often leading to import errors. To avoid this issue in your specific case where you want two classes to take instances of each other as constructor arguments, consider the following approaches:

1. Shared Reference Module:

Create a separate module (e.g., reference.py) that imports both classes and provides references to each:

# reference.py
from class_a import ClassA
from class_b import ClassB

Then, in your class definitions, import the reference module and use it to access instances of the other class:

# class_a.py
from reference import ClassB

class ClassA:
    def __init__(self, class_b_instance):
        self.class_b_instance = class_b_instance

2. Abstract Base Class (ABC):

Define an abstract base class for the common interface between your classes, and have both classes implement this interface:

# abc.py
from abc import ABC, abstractmethod

class Base(ABC):
    @abstractmethod
    def get_instance(self):
        pass

# class_a.py
from abc import ABC
from reference import ClassB

class ClassA(Base):
    def __init__(self, class_b_instance):
        self.class_b_instance = class_b_instance

    def get_instance(self):
        return self.class_b_instance

3. Adapter Pattern:

Create an adapter class that converts instances of one class to the interface of the other class:

# adapter.py
class Adapter:
    def __init__(self, instance):
        self.instance = instance

    def get_instance(self):
        return self.instance

Then, in your class definitions, use the adapter to wrap instances of the other class:

# class_a.py
from adapter import Adapter
from reference import ClassB

class ClassA:
    def __init__(self, class_b_instance):
        self.class_b_instance = Adapter(class_b_instance)

The above is the detailed content of How to Avoid Circular Imports When Classes Depend on Each Other?. For more information, please follow other related articles on the PHP Chinese website!