Augmented Assignment question

Bob Gailer bgailer at alum.rpi.edu
Thu Jul 17 00:52:29 CEST 2003


At 06:13 PM 7/16/2003 +0000, 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?

I suggest: use a list instead of separate counter variables, and update the 
list within the function.

counters = [0]*4 # initialize list
def checkdoc(self, document, counters):
     blen = document['length']
     bates = document['obates']
     for bat in bates:
         if len(bat) == 2 * blen:
             x = 0
         if len(bat) == blen - 1:
             x = 1
         if len(bat) == blen:
             x = 2
         else:
             x = 3 #
         counters[x] += 1

Bob Gailer
bgailer at alum.rpi.edu
303 442 2625
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