Is there a decorator to simply cache function return values?

Starting from Python 3.2 there is a built-in decorator: @functools.lru_cache(maxsize=100, typed=False) Decorator to wrap a function with a memoizing callable that saves up to the maxsize most recent calls. It can save time when an expensive or I/O bound function is periodically called with the same arguments. Example of an LRU cache for computing Fibonacci … Read more

What’s the ‘@’ (at symbol) in the Redux @connect decorator?

The @ symbol is in fact a JavaScript expression currently proposed to signify decorators: Decorators make it possible to annotate and modify classes and properties at design time. Here’s an example of setting up Redux without and with a decorator: Without a decorator import React from ‘react’; import * as actionCreators from ‘./actionCreators’; import { … Read more

How to get method parameter names?

Take a look at the inspect module – this will do the inspection of the various code object properties for you. >>> inspect.getfullargspec(a_method) ([‘arg1’, ‘arg2’], None, None, None) The other results are the name of the *args and **kwargs variables, and the defaults provided. ie. >>> def foo(a, b, c=4, *arglist, **keywords): pass >>> inspect.getfullargspec(foo) … Read more

How do the Proxy, Decorator, Adapter, and Bridge Patterns differ?

Proxy, Decorator, Adapter, and Bridge are all variations on “wrapping” a class. But their uses are different. Proxy could be used when you want to lazy-instantiate an object, or hide the fact that you’re calling a remote service, or control access to the object. Decorator is also called “Smart Proxy.” This is used when you … Read more

Experimental decorators warning in TypeScript compilation

I’ve to add the following in the settings.json file of vscode to remove the warning. “javascript.implicitProjectConfig.experimentalDecorators”: true VSCode -> Preferences -> Settings UPDATE As Clepsyd pointed out, this setting had been deprecated. You need to use now “js/ts.implicitProjectConfig.experimentalDecorators”:true

Decorators with parameters?

The syntax for decorators with arguments is a bit different – the decorator with arguments should return a function that will take a function and return another function. So it should really return a normal decorator. A bit confusing, right? What I mean is: def decorator_factory(argument): def decorator(function): def wrapper(*args, **kwargs): funny_stuff() something_with_argument(argument) result = … Read more

What does functools.wraps do?

When you use a decorator, you’re replacing one function with another. In other words, if you have a decorator def logged(func): def with_logging(*args, **kwargs): print(func.__name__ + ” was called”) return func(*args, **kwargs) return with_logging then when you say @logged def f(x): “””does some math””” return x + x * x it’s exactly the same as … Read more

How does the @property decorator work in Python?

The property() function returns a special descriptor object: >>> property() <property object at 0x10ff07940> It is this object that has extra methods: >>> property().getter <built-in method getter of property object at 0x10ff07998> >>> property().setter <built-in method setter of property object at 0x10ff07940> >>> property().deleter <built-in method deleter of property object at 0x10ff07998> These act as … Read more

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