namedtuples anamoly

[Gary Herron]

On 10/17/2018 11:13 PM, me.vinob at gmail.com wrote:
> Hi,
>
> I tried using namedtuples and just found a behaviour which I am not able to
> conclude as correct behaviour.
>
> from collections import namedtuple
>
> (n, categories) = (int(input()), input().split())
> Grade = namedtuple('Grade', categories)
> Grade.ID = 1
> #print(Grade.ID)
> ob = Grade(10, 50)
> print(ob.ID)
> print(ob.MARKS)
> ob1 = Grade(20, 100)
> print(ob1.ID)
>
> 2
> ID MARKS
> 1
> 50
> 1
> 100
>
>
> If we set GRADE.ID =1 ,

Whoa!  Don't do that.  The Grade object created with the namedtuple call 
is a class, and part of it's internal implementation is stored in 
Grade.ID.  Try these lines:

 >>> print(Grade)
<class '__main__.Grade'>
 >>> print(Grade.ID)
<property object at 0x7f1867e877c8>
 >>>

By reassigning Grade.ID, you are sabotaging the internals of the class.  
Without looking at those internals, it's not really a surprise that 
things stop working after you destroy the <property object ...>  it so 
carefully stored in Grade.ID.


So now the real question is:  What were you trying to accomplish with 
the assignment?  Tell us, and let's see if we can find a way to 
accomplish yor goal without wrecking the internals of the Grade class.


Gary Herron


> it has impact on all variables. Is this behaviour
> just like class variable and it has global scope.
> I expected ob.ID and ob1.ID to be 10.
>
> Correct me if Iam wrong.
> Appreciate any quick response.
>
> Kind Rgds,
> Vinu

-- 
Dr. Gary Herron
Professor of Computer Science
DigiPen Institute of Technology
(425) 895-4418