{"id":5781,"library":"lazy","title":"Lazy Attributes for Python Objects","description":"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.","status":"active","version":"1.6","language":"python","source_language":"en","source_url":"https://github.com/stefanholek/lazy","tags":["decorator","lazy","lazy attribute","descriptor","property"],"install":[{"cmd":"pip install lazy","lang":"bash","label":"Install latest version"}],"dependencies":[],"imports":[{"symbol":"lazy","correct":"from lazy import lazy"}],"quickstart":{"code":"from lazy import lazy\n\nclass Foo(object):\n    @lazy\n    def bar(self):\n        print(\"computing bar\")\n        return 42\n\nf = Foo()\nprint(f.bar)\nprint(f.bar)","lang":"python","description":"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."},"warnings":[{"fix":"Ensure the underlying data is immutable or clear and re-initialize the object if fresh computation is required.","message":"Lazy 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.","severity":"gotcha","affected_versions":"All"},{"fix":"Avoid relying on side effects for subsequent accesses or ensure side effects are idempotent and safe to run once.","message":"Any 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.","severity":"gotcha","affected_versions":"All"},{"fix":"Implement explicit locking or ensure thread synchronization if the lazy attribute is accessed by multiple threads before its initial computation.","message":"The 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.","severity":"gotcha","affected_versions":"All"}],"env_vars":null,"search_vec":"'1.6':10 '2023':64 'absolut':47 'access':27 'activ':53 'allow':16 'attribut':2,18,68 'cach':30 'cadenc':58 'comput':21,45 'decor':65 'defer':42 'descriptor':14,69 'effici':38 'enabl':37 'expens':44 'first':26 'latest':61 'lazi':1,7,66,67 'librari':8 'maintain':51 'necessari':48 'object':5,17 'potenti':43 'project':50 'properti':70 'provid':11 'python':4,13 'rapid':56 'releas':57 'resourc':39 'result':32 'retriev':35 'subsequ':34 'though':54 'updat':62 'usag':40 'version':9","created_at":"2026-04-14T05:06:50.844947+00:00","updated_at":"2026-04-16T16:10:25.448935+00:00","problems":[{"fix":"Install the library using pip: `pip install lazy`","cause":"The 'lazy' library has not been installed in the current Python environment or is not accessible on the PYTHONPATH.","error":"ModuleNotFoundError: No module named 'lazy'"},{"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.","cause":"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.","error":"AttributeError: can't set attribute"},{"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()`).","cause":"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.","error":"TypeError: 'dict' object is not callable"}],"ecosystem":"pypi","meta_description":null,"install_score":null,"quickstart_score":null,"quickstart_tag":null,"pypi_latest":"2.0","cli_name":"","cli_version":null,"type":"library","homepage":null,"github":"https://github.com/stefanholek/lazy","docs":"https://lazy.readthedocs.io/en/stable/","changelog":null,"pypi":"https://pypi.org/project/lazy/","npm":null,"openapi_spec":null,"status_page":null,"smithery":null,"categories":["serialization"],"base_url":null,"auth_type":null,"provenance":{"verified_status":"passing","verified_at":"2026-06-28","last_verified":"2026-08-31","next_check":"2026-07-28","install_tag":null}}