Composition of functions

[Chris Rebert]

On Wed, Jun 30, 2010 at 9:09 PM, Zubin Mithra <zubin.mithra at gmail.com> wrote:
> Hello,
>
>> >>> y=list(x).reverse()
>> >>> print y
>> None
>
>>>> L = ["a", "b", "c"]
>>>> L.reverse()
>>>> L
> ["c", "b", "a"]
>
> As you can see, L.reverse() performs the operation on itself and returns
> nothing. Hence, the return type None.
>
> Instead of
>
> y=''.join(list(x).reverse())
>
> you should probably do,
>
>>>> t = list(x).reverse()
>>>> y = ''.join(t)

Er, I don't think you thought that one entirely through (/ tried it out):

chris at morpheus ~ $ python
Python 2.6.5 (r265:79063, May 25 2010, 18:21:57)
[GCC 4.2.1 (Apple Inc. build 5659)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> x = "hello"
>>> t = list(x).reverse()
>>> print t
None
>>> ''.join(t)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError

Cheers,
Chris
--
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