[Tutor] Having trouble with a dictionary of lists

[Emile van Sebille]

On 9/3/2009 11:01 AM William Witteman said...
> I am trying to create a CSV file of sorted similar lists, arranged so
> that differences are easily compared in a spreadsheet.  I am
> encountering the following error, however:
> 
> IndexError: list assignment index out of range
> 
> On the indicated line below.  I understand the error, but I don't
> understand why I am getting it.  Can anyone shed some light on this?
> Thanks.
> 
> #!/usr/bin/python
> 
> """
> Take a collection of lists, combine them into one list, deleting duplicates.
> Sort the list and use it as the leftmost column of a table.  Then put each 
> lists contents into the table, one per column, with the elements aligned
> with the leftmost (index) column.
> 
> """
> 
> import os, sys, csv
> 
> def cmpss(filename,*sslists):
>   """Write a CSV file from the collection of lists."""
> 
>   if os.path.exists(filename):
>     print("%s exists: please choose another filename." % filename)
>     sys.exit(1)
>   else:
>     try:
>       fn = csv.writer(open(filename, "w"))
>     except IOError:
>       print("There is a problem opening the requested file.  Sorry.")
>       sys.exit(1)
> 
>   termdict = {}
> 
>   for sslist in sslists:
>     for term in sslist:
>       termdict[term] = ""
>   
>   termlist = termdict.keys()
>   termlist.sort()
> 
>   sortedtermdict = {}
>   number_of_commas = 1 - len(sslists)
>   
>   for term in termlist:
>     sortedtermdict[term] = ["" for x in range(number_of_commas)]
> 
>   for sslist in sslists:
>     counter = 0
>     for term in sslist:
> # The line below is where my program barfs.
>       sortedtermdict[term][counter] = term
>     counter = counter + 1

This increases counter once for each term in sslist, but
sortedtermdict[term]'s length is a function of the number_of_commas, so 
when termlist if longer then number_of_commas, you'd get the error.

HTH,

Emile


> 
>   for row in sortedtermdict:
>     fn.writerow(row)
>