doctest fails to NORMALIZE_WHITESPACE ?

[Tim Peters]

[David MacKay]
> Hello, I'm a python-list newbie. I've got a question about doctest; perhaps
> a bug report.

As things will turn out, it's just a question.  That's common for newbies :-)

> I really like doctest, but sometimes doctest gives a failure when the output
> looks absolutely fine to me -- indeed, even after I have gone to considerable
> effort to make my documentation match the output perfectly.
>
> http://www.aims.ac.za/~mackay/python/compression/huffman/Huffman3.py
>
> The above file is an example.
>
> It's self-contained, so you can plop it into emacs and hit C-cC-c to run the
> doctests. One of them fails.
> The piece of source code concerned is here:
>
>     >>> c = []; \
>         c.append(node(0.5,1,'a')); \
>         c.append(node(0.25,2,'b')); \
>         c.append(node(0.125,3,'c')); \
>         c.append(node(0.125,4,'d')); \
>         iterate(c) ; reportcode(c)               # doctest: +NORMALIZE_WHITESPACE, +ELLIPSIS

I'd probably write that more like so:

>>> c = [node(0.5,1,'a'), node(0.25,2,'b'), node(0.125,3,'c'),
node(0.125,4,'d')]
>>> iterate(c)
>>> reportcode(c)  # doctest [etc]

When Python doesn't "look clean", it's not Python -- and backslash
continuation & semicolons often look like dirt to the experienced
Python's eye.

>     #Symbol     Count   Codeword
>     a         (0.5)     1
>     b         (0.25)    01
>     c         (0.12)    000
>     d         (0.12)    001
>     """
>
> And the output is:
>
> Failed example:
>     c = [];         c.append(node(0.5,1,'a'));         c.append(node(0.25,2,'b'));         c.append(node(0.125,3,'c'));         c.append(node(0.125,4,'d'));         iterate(c) ; reportcode(c)               # doctest: +NORMALIZE_WHITESPACE, +ELLIPSIS
> Expected:
>     #Symbol     Count   Codeword
>     a         (0.5)     1
>     b         (0.25)    01
>     c         (0.12)    000
>     d         (0.12)    001
> Got:
>     <__main__.internalnode instance at 0xb7aee76c>

Well, there you go, right?  There was certainly no

    <__main__.internalnode instance at 0xb7aee76c>

line in the expected output.  I don't know whether you _want_ to see
that line or not, but the doctest said you don't.  That's why the test
fails.  If you do want to see it, add, e.g.,

    <__main__.internalnode instance at 0x...>

as the first line of the expected output.

>     #Symbol     Count   Codeword
>     a   (0.5)   1
>     b   (0.25)  01
>     c   (0.12)  000
>     d   (0.12)  001

You have another problem here, alas:  whether a "%2.2g" format rounds
0.125 to "0.12" or "0.13" varies across platforms.  For example, if
you had run this on Windows, you would have seen:

     c   (0.13)  000
     d   (0.14)  001

for the last two lines.

> I have tried numerous tweaks, and am at a loss. I am wondering whether there
> is some big in doctest involving the "#" character in the output.
> Or maybe I made some silly mistake.

I think we're ready to vote on that now ;-)

> Any advice appreciated!
>
> Many thanks again to the authors of doctest, it gives a great feeling
> to write code in the way that doctest encourages. :-)

You're welcome!