lazy

library2.0pypypi✓ verified 22d ago

The `lazy` library (version 1.6) provides a Python descriptor that allows object attributes to be computed only when they are first accessed, and then caches the result for subsequent retrievals. It enables efficient resource usage by deferring potentially expensive computations until absolutely necessary. The project maintains an active, though not rapid, release cadence, with the latest update in 2023.

serialization

pip install lazy

github ↗package ↗docs ↗

INSTALL

IMPORT

SIG · LAZY

lazy

serializationpythonv2.0

Install

1.5s avg

Import

—

Disk

16MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v2.0 · pip install

no network on importno background threads

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

py 3.10–3.95 runs

installs and imports cleanly · install 0.0s · import 0.000s · 17.8MB

glibc

py 3.10–3.95 runs

installs and imports cleanly · install 1.5s · import 0.000s · 18MB

16MB installed

● package 16MB

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

lazy

✓ from lazy import lazy

Demonstrates the basic usage of the `@lazy` decorator on a method, turning it into a lazy-loaded, cached attribute. The computation ('computing bar') runs only on the first access.

from lazy import lazy class Foo(object): @lazy def bar(self): print("computing bar") return 42 f = Foo() print(f.bar) print(f.bar)

Debug

Known issues

gotchaLazy attributes are computed only once and then cached. If the underlying data or state that the lazy attribute depends on changes after its first access, the attribute will continue to return the stale cached value.

fix

Ensure the underlying data is immutable or clear and re-initialize the object if fresh computation is required.

affects: All

gotchaAny side effects within the method decorated with `@lazy` (e.g., logging, modifying other object state) will occur only on the first access when the attribute is initially computed. Subsequent accesses will retrieve the cached value without re-executing the method.

fix

Avoid relying on side effects for subsequent accesses or ensure side effects are idempotent and safe to run once.

affects: All

gotchaThe library's `@lazy` decorator may not be inherently thread-safe. If multiple threads concurrently access a lazy attribute for the very first time, it could lead to the underlying computation running multiple times or result in a race condition for setting the cached value.

fix

Implement explicit locking or ensure thread synchronization if the lazy attribute is accessed by multiple threads before its initial computation.

affects: All

Errors

Common errors & fixes

ModuleNotFoundError: No module named 'lazy'

The 'lazy' library has not been installed in the current Python environment or is not accessible on the PYTHONPATH.

fix

Install the library using pip: `pip install lazy`

AttributeError: can't set attribute

An attempt was made to reassign a value directly to an attribute that was decorated with `@lazy` after it had already been accessed and its value computed. The `@lazy` descriptor typically makes attributes read-only after their initial lazy evaluation.

fix

Avoid direct reassignment to a `@lazy` attribute. If the value needs to change, consider if `@lazy` is the appropriate tool for that attribute, or implement a mechanism to invalidate the cached value if the library provides one.

TypeError: 'dict' object is not callable

A method decorated with `@lazy` was accessed once, which computed and cached its result (e.g., a dictionary). Subsequent attempts treated this cached *result* as if it were still the original callable method, leading to a `TypeError` when trying to call a non-callable object.

fix

Once a `@lazy` attribute has been accessed, its value is cached. To retrieve the cached value, access the attribute directly (e.g., `obj.attribute_name`). Do not attempt to call it like a method (e.g., `obj.attribute_name()`).

Upgrade

Version history

2.0latest on PyPI · released Jul 4, 2026

Audit

Dependencies

No dependency data recorded yet.

Agent activity

7 hits · last 30 days

node

Resources

githubhttps://github.com/stefanholek/lazy ↗

packagehttps://pypi.org/project/lazy/ ↗

docshttps://lazy.readthedocs.io/en/stable/ ↗