Use a dependency injection framework

Oct 13, 2025 by magicalceylontours.com 149 views

Introduction

In the world of programming, side effects are a common phenomenon that can lead to unexpected behavior and make code harder to reason about. One of the most common sources of side effects is imports. When we import a module, we are not just importing the code, but also the side effects that come with it. In this article, we will explore how to eliminate import side effects and make our code more predictable and maintainable.

What are Import Side Effects?

Import side effects occur when an import statement has an effect on the program's behavior, other than just importing the code. This can happen when an import statement executes some code, sets up some global state, or even modifies the environment. Import side effects can be difficult to detect and debug, as they often manifest themselves in unexpected ways.

Example: Import Side Effects in PyTorch

Let's take the example of PyTorch, a popular deep learning library. When we import PyTorch, it sets up some global state, such as the random number generator, and also executes some code to initialize the library. This can lead to side effects, such as changing the random number generator's state or modifying the environment.

import torch
from effectful.ops.syntax import defop

x = defop(torch.Tensor)

t = torch.randn((2, 3))[x()]

In this example, the torch import statement sets up some global state and executes some code to initialize the library. This can lead to side effects, such as changing the random number generator's state or modifying the environment.

Why Eliminate Import Side Effects?

Eliminating import side effects is important for several reasons:

Predictability: When we eliminate import side effects, we can predict the behavior of our code with more certainty. This makes it easier to reason about our code and debug issues.
Maintainability: Import side effects can make our code harder to maintain, as they can lead to unexpected behavior and make it difficult to understand how our code works.
Reusability: When we eliminate import side effects, we can reuse our code more easily, as it is less likely to have unexpected behavior.

How to Eliminate Import Side Effects?

So, how can we eliminate import side effects? Here are some strategies:

Use lazy imports: Instead of importing a module directly, we can use lazy imports to delay the import until it is actually needed.
Use import hooks: Import hooks allow us to execute code before or after an import statement is executed. We can use this to set up some global state or execute some code to initialize the library.
Use a dependency injection framework: A dependency injection framework allows us to inject dependencies into our code, rather than importing them directly. This can help to eliminate import side effects.

Lazy Imports

Lazy imports are a great way to eliminate import side effects. Instead of importing a module directly, we can use lazy imports to delay the import until it is actually needed.

import importlib

def lazy_import(module_name):
    return importlib.import_module(module_name)

torch = lazy_import('torch')

In this example, we use the importlib module to delay the import of the torch module until it is actually needed.

Import Hooks

Import hooks allow us to execute code before or after an import statement is executed. We can use this to set up some global state or execute some code to initialize the library.

import importlib
import sys

def import_hook(module_name):
    # Set up some global state
    sys.random.seed(42)
    # Execute some code to initialize the library
    torch.randn((2, 3))

sys.meta_path.insert(0, import_hook)

In this example, we use the importlib module to execute some code before the torch module is imported.

Dependency Injection Framework

A dependency injection framework allows us to inject dependencies into our code, rather than importing them directly. This can help to eliminate import side effects.

import effectful

class TorchDependency:
    def __init__(self):
        self.torch = torch

    def get_torch(self):
        return self.torch

torch_dependency = TorchDependency()

def get_torch():
    return torch_dependency.get_torch()

t = get_torch().randn((2, 3))

In this example, we use a dependency injection framework to inject the torch dependency into our code.

Conclusion

Introduction

In our previous article, we explored how to eliminate import side effects and make our code more predictable and maintainable. In this article, we will answer some frequently asked questions about eliminating import side effects.

Q: What are import side effects?

A: Import side effects occur when an import statement has an effect on the program's behavior, other than just importing the code. This can happen when an import statement executes some code, sets up some global state, or even modifies the environment.

Q: Why are import side effects a problem?

A: Import side effects can lead to unexpected behavior and make code harder to reason about. They can also make our code harder to maintain and reuse.

Q: How can I eliminate import side effects?

A: There are several ways to eliminate import side effects, including:

Lazy imports: Instead of importing a module directly, we can use lazy imports to delay the import until it is actually needed.
Import hooks: Import hooks allow us to execute code before or after an import statement is executed. We can use this to set up some global state or execute some code to initialize the library.
Dependency injection frameworks: A dependency injection framework allows us to inject dependencies into our code, rather than importing them directly.

Q: What are lazy imports?

A: Lazy imports are a way to delay the import of a module until it is actually needed. This can help to eliminate import side effects by preventing the module from being imported unnecessarily.

Q: How do I use lazy imports?

A: To use lazy imports, we can use the importlib module to delay the import of a module. For example:

import importlib

def lazy_import(module_name):
    return importlib.import_module(module_name)

torch = lazy_import('torch')

Q: What are import hooks?

A: Import hooks are a way to execute code before or after an import statement is executed. This can help to eliminate import side effects by setting up some global state or executing some code to initialize the library.

Q: How do I use import hooks?

A: To use import hooks, we can use the sys.meta_path attribute to insert a hook into the import process. For example:

import importlib
import sys

def import_hook(module_name):
    # Set up some global state
    sys.random.seed(42)
    # Execute some code to initialize the library
    torch.randn((2, 3))

sys.meta_path.insert(0, import_hook)

Q: What are dependency injection frameworks?

A: Dependency injection frameworks are a way to inject dependencies into our code, rather than importing them directly. This can help to eliminate import side effects by making our code more modular and reusable.

Q: How do I use dependency injection frameworks?

A: To use dependency injection frameworks, we can use a library such as effectful to inject dependencies into our code. For example:

import effectful

class TorchDependency:
    def __init__(self):
        self.torch = torch

    def get_torch(self):
        return self.torch

torch_dependency = TorchDependency()

def get_torch():
    return torch_dependency.get_torch()

t = get_torch().randn((2, 3))

Conclusion

In conclusion, eliminating import side effects is an important step in making our code more predictable and maintainable. By using lazy imports, import hooks, and dependency injection frameworks, we can eliminate import side effects and make our code more modular and reusable.