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What is '@' for

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  What is '@' for fl <rxjwg98@gmail.com> - 2015-11-13 15:04 -0800
    Re: What is '@' for Chris Angelico <rosuav@gmail.com> - 2015-11-14 10:14 +1100
      Re: What is '@' for Tim Daneliuk <tundraBOGUS@tundraware.com> - 2015-11-13 17:43 -0600
    Re: What is '@' for Terry Reedy <tjreedy@udel.edu> - 2015-11-13 18:43 -0500
    Re: What is '@' for Dave Farrance <df@see.replyto.invalid> - 2015-11-14 09:14 +0000

#98778 — What is '@' for

Hi,

I read the following code snippet. A question is here about '@'.
I don't find the answer online yet.

What function is it here?

BTW, below is for printing out?
    """theta = logit^{-1}(a+b)"""

but I don't see it is printed when the following could have been called.

Are you sure it would be printed out?


Thanks,





.................
import pymc
import numpy as np

n = 5*np.ones(4,dtype=int)
x = np.array([-.86,-.3,-.05,.73])
alpha = pymc.Normal('alpha',mu=0,tau=.01)
beta = pymc.Normal('beta',mu=0,tau=.01)

@pymc.deterministic
def theta(a=alpha, b=beta):
    """theta = logit^{-1}(a+b)"""
    return pymc.invlogit(a+b*x)
    
d = pymc.Binomial('d', n=n, p=theta, value=np.array([0.,1.,3.,5.]),\
    observed=True)

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#98779

On Sat, Nov 14, 2015 at 10:04 AM, fl <rxjwg98@gmail.com> wrote:
> I read the following code snippet. A question is here about '@'.
> I don't find the answer online yet.
>
> What function is it here?
>
>
> @pymc.deterministic
> def theta(a=alpha, b=beta):
>     """theta = logit^{-1}(a+b)"""
>     return pymc.invlogit(a+b*x)

That's called a "function decorator". And now that you know the name,
you'll be able to find what it is online; as well as the Python docs,
there are a number of blog posts and other articles about it.

ChrisA

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#98781

On 11/13/2015 05:14 PM, Chris Angelico wrote:
> On Sat, Nov 14, 2015 at 10:04 AM, fl <rxjwg98@gmail.com> wrote:
>> I read the following code snippet. A question is here about '@'.
>> I don't find the answer online yet.
>>
>> What function is it here?
>>
>>
>> @pymc.deterministic
>> def theta(a=alpha, b=beta):
>>     """theta = logit^{-1}(a+b)"""
>>     return pymc.invlogit(a+b*x)
> 
> That's called a "function decorator". And now that you know the name,
> you'll be able to find what it is online; as well as the Python docs,
> there are a number of blog posts and other articles about it.
> 
> ChrisA
> 


One small point of order ... if you want to be precise, "@pymc.deterministic" is a *function decoration*.  The "decorator" is the function pymc.deterministic().

I know this is a fussy point, but this distinction is helpful when first learning the concept.

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#98780

On 11/13/2015 6:04 PM, fl wrote:

> I read the following code snippet. A question is here about '@'.
> I don't find the answer online yet.

Start with the index of the fine docs, which includes symbols.
https://docs.python.org/3/genindex-Symbols.html
'@' is near the end of the page.

> @pymc.deterministic
> def theta(a=alpha, b=beta):


-- 
Terry Jan Reedy

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#98800

fl <rxjwg98@gmail.com> wrote:

>I read the following code snippet. A question is here about '@'.
>I don't find the answer online yet.

I recommend this:

"Understanding Python Decorators in 12 Easy Steps!"

http://simeonfranklin.com/blog/2012/jul/1/python-decorators-in-12-steps/

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