lazysloth 0.0.6

A Python library for lazy and immutable variables.

lazysloth: Lazy and Immutable Variable Library for Python

lazysloth is a Python library designed to facilitate the use of lazy initialization patterns and immutable variables in Python applications. It provides two main functionalities through its LazyVariable and ImmutableVariable classes, allowing developers to defer expensive computations until absolutely necessary and to create variables that cannot be modified after initialization.

Status

WIP

Super early. At the time of writing this, this is not production-ready or anything close to that. This is a pet project I started 2 days ago. Hopefully, it will be production-ready in a few weeks.

Why

Too many things in Python evaluate at the time the code is loaded to memory, from global variables to the default values of function arguments. Sometimes, it's great; sometimes, it creates bugs that might be hard to find the first time or two before it's been burned into your experience. You can work around it with a slight refactor, which often involves wrapping some code in a function, a class, or a dictionary. I found myself writing these too many times in too many different projects, so I decided to write it once.

This time, my need came from wanting control over a singleton global variable holding the config.

I have a my_config.py file where I load my configuration, usually from files and environment variables.

from lazysloth import LazyVariable
from configlib import loader

settings = LazyVariable(loader.load_files, load_files=['settings.yml', 'settings.toml'])

from my_config import settings
from my_cli import get_current_run_cli_arguments



settings._kwargs['load_files'].append(
  get_current_run_cli_arguments()['--config-override-file']
)

Installation

pip install lazysloth

Replace lazysloth with the correct package name if published on PyPI or provide specific instructions if the library is to be installed directly from a source repository.

Features

• LazyVariable: Enables lazy initialization of variables, where the value is only computed upon the first access.
• ImmutableVariable: Wraps values in an immutable container, preventing changes after initialization.

Quick Start

Here's a quick example to get started with lazysloth, demonstrating the lazy loading behavior:

from lazysloth import LazyVariable

def expensive_computation():
    print("Expensive computation is now being executed...")
    return {"data": 42}

# Initialize a LazyVariable with the expensive computation.
lazy_var = LazyVariable(expensive_computation)

print("LazyVariable has been initialized.")
print("Accessing the variable to trigger computation...")

# The expensive computation is executed only upon this access.
print(lazy_var.data)  # Outputs: Expensive computation is now being executed... \n 42

Usage

def expensive_operation():
    print("Performing an expensive operation that takes time...")
    return "Result of the operation"

lazy_operation = LazyVariable(expensive_operation)

print("LazyVariable initialized, but expensive operation hasn't run yet.")
# At this point, the expensive operation has not been executed.

# Accessing the LazyVariable to trigger the expensive operation.
result = lazy_operation()
print(f"Operation result: {result}")
# Now, the expensive operation is executed, and its result is accessed.

Features

• LazyVariable: Enables lazy initialization of variables, where the value is only computed upon the first access.
• ImmutableVariable: Wraps values in an immutable container, preventing changes after initialization.

LazyVariable

LazyVariable is intended for situations where a variable's initialization is computationally expensive and not always necessary. The variable's value is computed only on the first access.

Initialization

lazy_var = LazyVariable(initializer_function, *args, **kwargs)

• initializer_function: A callable that returns the value to be lazily initialized.
• *args and **kwargs: Arguments passed to the initializer_function.

Access

Access attributes or items of the lazily initialized value as if LazyVariable were the value itself:

result = lazy_var.attribute
result = lazy_var['item']

Callable Support

If the lazily initialized value is callable, LazyVariable can be called directly:

result = lazy_var(*args, **kwargs)

ImmutableVariable

ImmutableVariable ensures that the wrapped value cannot be modified after initialization. It's useful for creating read-only data structures.

• value: The value to be made immutable.

Access

Access the immutable value's attributes or items directly:

result = immutable_var.attribute
result = immutable_var['item']

Attempting to modify the wrapped value results in an AttributeError.

Advanced Usage

• Resetting a LazyVariable: If your use case requires re-initializing a LazyVariable, you can extend its functionality to support resetting.

Contributing

Contributions to lazysloth are welcome! Please refer to the contributing guidelines for more information on how to submit pull requests, report issues, or request features.