change an element of a list

[bruno modulix]

Dirk Hagemann wrote:
> Hi!
> 
> I have a list of lists and in some of these lists are elements which I
> want to change.
> Here an example:
> lists=[('abc',  4102,  3572), ('def',  2707, 'None'), ('ghi',  'None', 4102)]
> 
> 'None' should be replaced by 0 or NULL or something else. 

Your list is a list of tuples, and what you want here is to replace an
element of a tuple - which is not directly possible since tuples are
immutables (but of course there's a way... !-)

> But as far as
> I know the replace function of the module string does not work for
> lists.

Nope, but you can still replace or modify an element of a list.

here a (very Q&D and probably naive and suboptimal) possible solution:

def my_replace(alist, target, replacement):
  """Takes a list of tuples and for each tuple
     'replace' target with 'replacement

  """
  for i, t in enumerate(alist):
    l = list(t)
    while target in l:
      l[l.index(target)] = replacement
    alist[i] = tuple(l)

my_replace(lists, 'None', 'NULL')

HTH


-- 
bruno desthuilliers
ruby -e "print 'onurb at xiludom.gro'.split('@').collect{|p|
p.split('.').collect{|w| w.reverse}.join('.')}.join('@')"
python -c "print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in 'onurb at xiludom.gro'.split('@')])"