newbie idiom question

[Alex Rice]

Something I keep getting tripped up about is that objects being
iterated in "for" statements cannot be modified.

I keep trying to do this:

      >>> eggs = [1,2,3]
      >>> for spam in eggs:
      ...	spam = 'cooked'
      ...
      >>> eggs
      [1, 2, 3]
      >>> 

The tutorial says this:

      If you need to modify the list you are iterating over, e.g., duplicate
      selected items, you must iterate over a copy. The slice notation makes
      this particularly convenient:

      >>> for x in a[:]: # make a slice copy of the entire list
      ...    if len(x) > 6: a.insert(0, x)
      ... 
      >>> a
      ['defenestrate', 'cat', 'window', 'defenestrate']

Understood, but what if you want to modify each element in a list?
What's the best way to do this in terms of speed and elegance? I guess
I just haven't seen a good example of this yet in Python

What I'm unfortunately used to is this, in Perl:

      @eggs = (1,2,3);
      foreach $spam (@eggs) {
	$spam = 'cooked'; 
      }
      print "@eggs";
      >>> cooked cooked cooked

Thanks,
Alex Rice