Accessing and Setting Event Loop Policy

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Use examples when they help make things clearer.

Today we’ll be diving into the world of event loop policies and how you can access and set them like a pro (or at least like someone who knows what they’re doing).

First off, why you might want to mess with these policies in the first place. Well, for starters, different event loops have their own strengths and weaknesses depending on your use case. For example, if you’re working with a lot of I/O-bound tasks (like reading from files or communicating over networks), you might prefer an event loop that optimizes for these operations. On the other hand, if you’re dealing with more CPU-intensive tasks (like running complex algorithms), you might want to choose an event loop that prioritizes processing power instead.

So how do we go about accessing and setting these policies? Well, it’s actually pretty simple! First, let’s take a look at the built-in policy:

# Import the asyncio library to access its functions
import asyncio

# Get the current default event loop policy
# and assign it to the variable "default_policy"
default_policy = asyncio.get_event_loop_policy()

# Print the default policy to the console
print(default_policy)

# The above code retrieves the current default event loop policy
# and prints it to the console. This allows us to see which policy
# is currently being used for handling CPU-intensive tasks.

This will print out something like “DefaultEventLoopPolicy” (depending on your version of Python). If you want to set a custom policy, it’s just as easy:

# Import the asyncio library
import asyncio
# Import the custom event loop policy from my_custom_event_loop.py
from my_custom_event_loop import MyCustomEventLoopPolicy

# Set the new policy for this process to be the custom one
asyncio.set_event_loop_policy(MyCustomEventLoopPolicy)

# Get the current event loop policy and assign it to the variable current_policy
current_policy = asyncio.get_event_loop_policy()
# Print the current policy, which should now be the custom one
print(current_policy)

In this example, we’re assuming that you have a file called “my_custom_event_loop.py” in the same directory as your script (or wherever it is that Python can find it). This file should contain a class named `MyCustomEventLoopPolicy`, which inherits from `asyncio.DefaultEventLoopPolicy` and overrides any methods you want to customize:

# Import the necessary modules
import asyncio # Importing the asyncio module for asynchronous programming
from typing import Any, Dict, List, Optional, Tuple # Importing the typing module for type annotations

# Create a custom event loop policy class that inherits from the DefaultEventLoopPolicy class
class MyCustomEventLoopPolicy(asyncio.DefaultEventLoopPolicy):
    
    # Define a method to get the event loop
    def get_event_loop(self) -> 'AbstractEventLoop':
        # Do something custom here!
        loop = super().get_event_loop() # Calling the get_event_loop method from the parent class
        # ...
        return loop # Returning the event loop

And that’s it! With these simple steps, you can easily access and set event loop policies in your Python code.

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