[Tutor] globals and map()

[Kent Johnson]

Luis N wrote:
> I'd appreciate some comments on my use of globals and the map function. 
> 
> import metakit
> import marshal
> 
> db = metakit.storage('addy.mk <http://addy.mk>',1)
> dbs = db.getas('dbs[db:S,marshal:B]')
> 
> def li(i):
>     i = i[:-2]
>     return i
> 
> def selectDB(f):
>     if f.has_key('db'):
>         d = []
>         d['db'] = f.get('db').value

The above line is not valid Python; list indices must be integers

>         id = dbs.find(d)
>         if id != -1:
>             global desc, vw, primaryKey
>             desc = marshal.loads(dbs[id].marshal)          
>             vw = db.getas('%s%s' % (dbs[id].db,desc))
>             desc = map(li,desc)

This use of map seems fine to me. You could also write it as a list comprehension which is more mainstream Python idiom and maybe more readable in this case as it is self-contained:
  desc = [ i[:-2] for i in desc ]

>             primaryKey = desc[0]            
>             return desc, vw, primaryKey   

I don't see the need for the global declaration; desc, vw, primaryKey are all assigned within this function and returned to the caller.

Kent
   
>         else:
>             error(-1)           
>     else:
>         error(select=None) 
> 
> 
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