doctest annoyance/puzzle

Steven D'Aprano steve at
Sun Sep 5 17:30:29 CEST 2010

I'm writing a "literate programming" document, example.txt, which mixes 
text and code in ReST format:

This is my excellent module for making spam. It has
one public function, ``make_spam``, which takes a 
single argument for how much spam to make:

    >>> from module import make_spam
    >>> make_spam(3)
    'spam spam spam'

If you ask for too little spam, you get a bonus:

    >>> make_spam(-3)
    'spam spam spam GLORIOUS SPAM!!!'

I run the doctests with:

python2.6 -m doctest examples.txt

and the first example passes, but the second fails with NameError: 
make_spam not defined.

I have a work-around, I do an import at the start of *every* doctest 
block, but that's ugly. More complex (realistic) examples sometimes need 
setup code, which I'd like to survive from one block to the next:

    >>> it = iter(make_spam(5).split())
    >>> next(it)

text goes here

    >>> next(it)

but of course that also fails. This surprises me, because doctests in 
functions or classes can mix descriptive text between tests without this 

Am I doing something wrong, or is doctest fundamentally broken when 
executing tests in a text file?


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