[Tutor] Changing lists in place

[Paul D. Eden]

Very true.

Paul

Kent Johnson wrote:
> Paul D. Eden wrote:
> 
>>Lists are mutable, you are right.
>>
>>But the code you gave does not change the list.  It changes the variable 
>>element which is separate from the list myList.
>>
>>If you want to change the list try something like this:
>>
>>mylist = [ 'One    ', '   two', '   three   ' ]
>>print mylist
>>newlist = []
>>for element in mylist:
>>     element = element.strip()
>>     newlist.append(element)
>>     print "<>" + element + "<>"
>>print newlist
>>
>>OR
>>
>>mylist = [ 'One    ', '   two', '   three   ' ]
>>print mylist
>>mylist = [element.strip() for element in mylist]
>>for element in mylist:
>>     print "<>" + element + "<>"
>>print mylist
> 
> 
> Neither of these changes the original list either. They both create new 
> lists with the desired contents. The second example binds the new list 
> to the old name, but it is still a new list. In many cases this is fine, 
> but the distinction is important. For example if you are writing a 
> function that modifies a list passed to it, these solutions won't work. 
> Bob's solution using enumerate() is the simplest way to modify a list in 
> place.
> 
> Kent
> 
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