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List:       python-list
Subject:    Re: Question about code writing '% i, callback'
From:       fl <rxjwg98 () gmail ! com>
Date:       2015-11-30 18:55:23
Message-ID: 53ef7ef4-cfec-4c91-a45c-5b847dde8fad () googlegroups ! com
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On Monday, November 30, 2015 at 12:02:57 PM UTC-5, Ian wrote:
> On Mon, Nov 30, 2015 at 10:44 AM, fl <ail.com> wrote:
> > I come across the following code snippet.
> >
> > for i in range(10):
> >     def callback():
> >         print "clicked button", i
> >     UI.Button("button %s" % i, callback)
> >
> > The content inside parenthesis in last line is strange to me.
> >
> > "button %s" % i, callback
> 
> These are the arguments being passed to UI.Button. The first argument is:
> 
>     "button %s" % i
> 
> This is an example of printf-style string formatting. See the link
> that Zachary posted.
> 
> The second argument is the function named callback.
> 
> > That is, the writing looks like recognized as three items when I try with a
> > class definition (it can run with this):
> >
> > class buibutton():
> >     print 'sd'
> >     def __nonzero__(self):
> >        return False
> >
> >     def Button(str, ii, callbackk):
> >
> >         return
> >
> >
> > Could you explain it to me?
> 
> How is this related to the example above?
> 
> Here, Button is defined as a method of a class. Since it's a method,
> the first parameter is the "self" parameter, which will implicitly
> take the value of the class instance that you're calling the Button
> method on. If you're trying to call this like above, then the second
> parameter "ii" will take the value of the string from the example
> above, and callbackk will take the value of the callback argument from
> above.
> 
> Thus, the method that you've defined has three parameters but only
> takes two explicit arguments.

"How is this related to the example above? 

Here, Button is defined as a method of a class. Since it's a method, 
the first parameter is the "self" parameter, which will implicitly 
take the value of the class instance that you're calling the Button 
method on."

Thanks Ian. I created the class because I want to use the original example
line 

 UI.Button("button %s" % i, callback)

Is there another way to use the above line without my class definition?
I do feel that my created class does not match well with the above line
because the first item "button %s" does not fit __self__ in the class.
My understanding about the above line code may not correct. This may further
result in not the original bug pops up.

Thanks,


 


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