Augmented Assignment question

[Adam Ruth]

In <215bhv0bnkn13eivh0s64ic5ml8obpgfg7 at 4ax.com> Doug Tolton  wrote:
> I have a function that returns a tuple:
> 
>     def checkdoc(self, document):
>         blen = document['length']
>         bates = document['obates']
> 
>         normal, truncated, semicolon = 0,0,0
>         for bat in bates:
>             if len(bat) == 2 * blen:
>                 semicolon += 1
>             if len(bat) == blen - 1:
>                 truncated += 1
>             if len(bat) == blen:
>                 normal += 1
> 
>         return normal, truncated, semicolon
> 
> on the other side I have 3 variables:
> normal, truncated and semicolon
> 
> I would like to be able to do an augmented assignment such as:
> 
> normal, truncated, semicol += self.checkdoc(mydoc)
> 
> however this returns the following error:
> SyntaxError: augmented assign to tuple not possible
> 
> I did some reading and it seems that an augmented assignment is
> specifically verboten on tuples and lists.  Is there a clean way to
> accomplish this?  I dislike in the extreme what I've resorted to:
> 
> fnormal, ftruncated, fsemicolon = 0,0,0
> 
> // loop through a file and process all documents:
> 	normal, truncated, semicolon = self.checkdoc(curdoc)
> 	fnormal += normal
> 	ftruncated += truncated
> 	fsemicolon += semicolon
> 
> This solution strikes me as inelegant and ugly.  Is there a cleaner
> way of accomplishing this?
> 
> Thanks in advance,
> Doug Tolton
> dougt at<remove this>case<remove this too>data dot com
> 

I don't think it's all that inelegant, and it's definitely clear.  I can 
see, though, why a one liner would seem a little cleaner.

Off the top of my head, I'd say to change your checkdoc function to this:

>     def checkdoc(self, document, normal=0, truncated=0, semicolon=0):
>         blen = document['length']
>         bates = document['obates']
>         for bat in bates:
>             if len(bat) == 2 * blen:
>                 semicolon += 1
>             if len(bat) == blen - 1:
>                 truncated += 1
>             if len(bat) == blen:
>                 normal += 1
> 
>         return normal, truncated, semicolon

And then call it like this:

> 	normal, truncated, semicolon = self.checkdoc(curdoc, normal, 
> truncated, semicolon)

As a side note, I wouldn't have thought that the augmented assign would 
work the way you tried to use it.  I would have thought that it would be 
analagous to the + operator and sequences:

>	x = [1,2,3]
>	y = [1,2,3]
>	x + y
[1,2,3,1,2,3]

So that the agumented form would be:

>	x = [1,2,3]
>	x += [1,2,3]
[1,2,3,1,2,3]

But I've never tried it before and didn't know that it didn't work with 
sequences.  You learn something new every day.

Adam Ruth