[Tutor] decorators -- treat me like i'm 6.. what are they.. why are they?
ahall at autodist.com
Wed Jul 6 17:25:58 EDT 2016
On Wed, Jul 6, 2016 at 4:56 PM, Alex Hall <ahall at autodist.com> wrote:
> On Wed, Jul 6, 2016 at 3:35 PM, bruce <badouglas at gmail.com> wrote:
>> Saw the decorator thread earlier.. didn't want to pollute it. I know, I
>> could google!
>> But, what are decorators, why are decorators? who decided you needed them!
> I thought of an example that may help. It's not a great example, but here
Say you own a bakery, and you employ Joe and me. You task me with taking
cookies from the kitchen and putting them in the display case in the
service area, which I do well. The problem is that I don't know what looks
appealing and what doesn't, so I keep putting cookies out that don't look
great. You can't teach something like that, it's just something you know.
Since you can't modify me to do my task in the way you want, you grab Joe
and have him help me. Instead of putting all the cookies out, I now have
Joe checking me before I place each one. Joe knows appealing, so is good at
this, but he's also usually busy up front so can't carry the cookies out
from the kitchen like I can.
Joe is the decorator, and I'm the function being decorated. Since I do my
task well, but lack a component you want, and since that component would be
hard to program, you find an existing version of the component (Joe) and
tell us to work together. Joe can modify my output before I return it,
letting him filter the appealing cookies out while I do the work of
carrying them up and setting out the ones Joe doesn't tell me to reject.
Hopefully this makes some sense.
> They're functions that modify the decorated function. If I make a function
> that performs a task, I might decorate with a logging function:
> def doSomething():
> #do stuff
> The logThis decorator could log the run, or modify the doSomething output,
> or do any number of tasks. To get that extra functionality, I need only
> decorate my own function. I see these a lot in Flask, a web framework,
> where they are used to define what parts of your website are handled by
> what functions, for instance. Basically, they let you extend what your
> functions do without needing to subclass anything.
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