Using namedtuples field names for column indices in a list of lists

Mon Jan 9 02:11:58 EST 2017

Steven D'Aprano wrote, on January 08, 2017 7:30 PM
>> On Sunday 08 January 2017 20:53, Deborah Swanson wrote:
>> > Steven D'Aprano wrote, on January 07, 2017 10:43 PM
>> No, I'm pretty sure that's not the case. I don't have access 
> to your CSV file, 
> but I can simulate it:
>> ls = [['Location', 'Date', 'Price'],
> ['here', '1/1/17', '1234'],
> ['there', '1/1/17', '5678'],
> ['everywhere', '1/1/17', '9821']
> ]
>> from collections import namedtuple
> lst = namedtuple('lst', ls[0])
>> print(type(lst))
> print(lst)
>>>> If you run that code, you should see:
>> <class 'type'>
> <class '__main__.lst'>
>>> which contradicts your statement:
>> 'lst' is a namedtuple instance with each of the column 
> titles as field names.

Yes, yes. In a careless moment I called a class an instance.
> and explains why you had to access the individual property 
> method `fget`: you 
> were accessing the *class object* rather than an actual named 
> tuple instance.

That code is deleted and long gone now, so I can't look at it in the
debugger, but yes, I'm pretty sure 'fget' is a class member.
> The code you gave was:
>> lst.Location.fget(l)
>> where l was not given, but I can guess it was a row of the 
> CSV file, i.e. an 
> individual record. So:
>> - lst was the named tuple class, a subclass of tuple
>> - lst.Location returns a property object
>> - lst.Location.fget is the internal fget method of the 
> property object.

And your point is? Perhaps I didn't express myself in a way that you
could recognize, but I understood all of that before I wrote to you, and
attempted to convey that understanding to you. Obviously I failed, if
you now think I need a lesson in what's going on here.
> I think Peter Otten has the right idea: create a list of 
> records with something 
> like this:
>>> Record = namedtuple('Record', ls[0])
> data = [Record(*row) for row in ls[1:])
>>> or if you prefer Peter's version:
>> data = [Record._make(row) for row in ls[1:])
>>> Half the battle is coming up with the right data structures :-)

Can't and wouldn't disagree with any part of that!
> -- 
> Steven
> "Ever since I learned about confirmation bias, I've been seeing 
> it everywhere." - Jon Ronson