gongliyu/decoutils

Utilities for writing decorators

decoutils: Utilities for writing decorators

Rationale

Python decorators are very useful. However, writing decorators with arguments is not straightforward. Take the following function as an example:

register_plugin(plugin, arg1=1):
    print('registering ', plugin.__name__, ' with arg1=', arg1)

This function registers a input function somewhere in the system. If this function could work as a decorator, that will be convinient. In order to make it a decorator, we just need it to return the input plugin trivially:

register_plugin(plugin, arg1=1):
    print('registering ', plugin.__name__, ' with arg1=', arg1)
    return plugin
    
@register_plugin
def plugin1(): pass

It is pretty easy so far. What if we want register_plugin works as a decorator with arguments? That's to say, we want to use it as:

@register_plugin(arg1=2)
def plugin2(): pass

In order to accomplish this goal, we need to wrap the function register_plugin so that it return a decorated plugin if the first input is a callable object, otherwise return a decorator with arguments. The decoutils.decorator_with_args is intend to abstract that wrapping, so that we can reuse it.

Installation

Install from PyPI

pip install decoutils

Install from Anaconda

conda install -c liyugong decoutils

Simple example

Basically, decorator_with_args enables a ordinary decorator function to be a decorator with arguments.

@decorator_with_args
def register_plugin(plugin, arg1=1):
    print('registering ', plugin.__name__, ' with arg1=', arg1)
    return plugin
    
@register_plugin(arg1=10)
def plugin1(): pass

Moreover, decorator_with_args itself is also a decorator with arguments: one argument return_original which can be used to convert a non-decorator function to be a decorator

@decorator_with_args
def register_plugin(plugin, arg1=1):
    print('registering ', plugin.__name__, ' with arg1=', arg1)
    # Note here the function does not return the plugin, so it cannot work as a decorator originally
    
@register_plugin(arg1=10)
def plugin1(): pass

decorator_with_args can also convert a function to decorator whose decorating target is not its first argument, e.g.

decorator_with_args(target_pos=1)
def register_plugin(arg1, plugin):
    return plugin
    
@register_plugin(100) # plugin2 will be registered with arg1=100
def plugin2(): pass

return_original control whether the resultant decorator return the original plugin, or the result of function register_plugin.

License

The decoutils package is released under the MIT License

Documentation

https://decoutils.readthedocs.io