Why this behavior? (was: Stupid Lambda Tricks)

[Simon Brunning]

> From:	Jonathan Gardner [SMTP:jgardn at alumni.washington.edu]
> I've always wondered:
> 
> >>> "abc".upper()
> "ABC"
> >>> [3,1,2].sort()
> < nothing >
> 
> Why is that? Is it just easier to implement it this way, or is there some 
> sound philosophical reason for this?
 
The latter.

Strings are immutable, so methods which 'change' them must in fact be
creating a new string. This has to be returned by the method - otherwise,
where would it go?

Lists are mutable. Methods actually *do* change them - 'sort' sorts the list
in place. To remind you of this fact, nothing is returned by the method. If
'sort' *did* return the sorted list, you could do:

spam = [3, 2, 1]
eggs = spam.sort()

Now, you might think that eggs is sorted and spam isn't, but if fact, spam
*is* sorted.

So instead, sort returns nothing, and you'll get a runtime error of some
sort in no time, and you'll find the problem quickly.

Cheers,
Simon Brunning
TriSystems Ltd.
sbrunning at trisystems.co.uk




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