@ operator at the beginning of the line in python

Question

I'm trying to understand what does this operator @, uses in python. I saw something about matrix multipication , but this is sure not the case,I'll give an example:

 @property
 def num_reserved_ids(self):
    return 0

Or:

 @registry.register_problem()
 class LibrispeechNoisy(Librispeech):

Last one:

@registry.register_hparams
def transformer_librispeech_tpu_v1():
"""HParams for training ASR model on Librispeech on TPU v1."""
    hparams = transformer_librispeech_v1()
    update_hparams_for_tpu(hparams)

Registry is another file that is used in the program.register_hparams is a function inside. Don't know what "property" is, but even registry that I know what it is, I can't understand the purpose of the operator :@, I'm a bit slow, sorry for that :/ ..

If anyone wants to look for some more code you can check tensor2tensor library: https://github.com/tensorflow/tensor2tensor/tree/master/tensor2tensor

It's called a _decorator_ but your examples are a bit diverse for me to think how to answer this. — roganjosh, Aug 08 '18 at 11:48
`numpy` uses `@` as the matrix multiplication sign. standard Python uses it for [decorators](https://www.thecodeship.com/patterns/guide-to-python-function-decorators/). — Ma0, Aug 08 '18 at 11:48
I didn't duplicate on purpose,if that's what you're saying, I searched and nothing returned, but thanks for another source of information. — albert1905, Aug 08 '18 at 11:59
@albert1905 nobody suggested that you did, and please don't take duplicates as some indication you did something wrong. You found a different way of wording some problem, so it will act as a signpost to the correct explanation :) Now a different combination of words in a Google search are more likely to get someone to the answer they want. — roganjosh, Aug 08 '18 at 12:01

score 2 · Accepted Answer · answered Aug 08 '18 at 11:49

I think what you are looking for is called PythonDecorators

Here is the Wiki For Python Decorators

A Python decorator is a specific change to the Python syntax that allows us to more conveniently alter functions and methods (and possibly classes in a future version). This supports more readable applications of the DecoratorPattern but also other uses as well.

The best way to understand them is from Corey Schafer's Video on Python Decorators

@ operator at the beginning of the line in python

1 Answers1