A Python library for lazy and immutable variables.
Project description
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 theinitializer_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 aLazyVariable
, 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.
Project details
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