Databases
StackOverflow2013
Postsdbo
PObehaviour of descriptor concept in python (confusing)
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PObehaviour of descriptor concept in python (confusing)
    primarykey
    data
    text
    <p>I understood python descriptor but I have a little confusion about this..</p> <p>if you have a class descriptor as follows</p> <pre><code>class Descriptor(object): def __get__(self, instance, owner): print 'getting' return self.value def __set__(self, instance, value): print 'setting' self.value = value def __delete__(self, instance): print 'deleting' del self.value </code></pre> <p>and a class whose attributes we want to manage is something like this..</p> <pre><code>class Test(object): name = Descriptor() def __init__(self, name): print 'init test' self.name = name </code></pre> <p>when I create object of class Test and do something it gives me answer like this...</p> <pre><code>t = Test('abc') init test setting &gt;&gt;&gt; t.name getting 'abc' &gt;&gt;&gt; del t.name deleting &gt;&gt;&gt; t &lt;__main__.Test object at 0x013FCCD0&gt; &gt;&gt;&gt; t.name getting </code></pre> <p>Now I want to have a class Test1 something like this..</p> <pre><code>class Test1(object): def __init__(self, value): print 'init test1' self.name = Descriptor() self. value = value </code></pre> <p>and if I create object of Test1 and try to access attribute of instance of Test1, I get output something like this..</p> <pre><code>t1 = Test1(12) t1.name &gt;&gt;&gt; getting &gt;&gt;&gt; 12 &gt;&gt;&gt; t1.name = 30 &gt;&gt;&gt; setting </code></pre> <p>Q 1) my question is that is this name attribute declared in init of Test1, is bound to instance of Test1 or not... because when I try to get attribute dictionary of t1, it return empty dict...</p> <pre><code>t1.__dict__ &gt;&gt;&gt; {} </code></pre> <p>same for class Test's instance t</p> <pre><code> t.__dict__ &gt;&gt;&gt; {} </code></pre> <p>When I add a new attribute to any of these instances, like this... </p> <pre><code> t.some = 'some' &gt;&gt;&gt; t1.some = 'some' </code></pre> <p>and again if I try to access attribute dictionary it gives me only which I have added just now.. now all instance attribute </p> <pre><code>t.__dict__ &gt;&gt;&gt; {'some': 'some'} &gt;&gt;&gt; t1.__dict__ &gt;&gt;&gt; {'some': 'some'} </code></pre> <p>Q 2) So what is the difference between instance attributes defined in init (like variable name and value in class Descriptor and Test) and attributes defined after instance creation (like variable t.some).</p> <p>Q 3) How class Test is different than class Test1. </p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. UStailor_raj
    1. UStailor_raj
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. PObehaviour of descriptor concept in python (confusing)
      1. UStailor_raj
      1. VTFavorite
    2. VO
      singulars
      1. PObehaviour of descriptor concept in python (confusing)
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI don't have quite the same behaviour here - what I get is the expected behaviour : >>> from desc import * >>> t1 = Test1(12) init test1 >>> t1.name <desc.Descriptor object at 0x143d450> >>> t1.__dict__ {'name': <desc.Descriptor object at 0x143d450>, 'value': 12}
      singulars
      1. PObehaviour of descriptor concept in python (confusing)
      1. USbruno desthuilliers
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload