string quoting issues in doctests

Question

When I run doctests on different Python versions (2.5 vs 2.6) and different plattforms (FreeBSD vs Mac OS) strings get quoted differently:

Failed example:
    decode('{"created_by":"test","guid":123,"num":5.00}')
Expected:
    {'guid': 123, 'num': Decimal("5.00"), 'created_by': 'test'}
Got:
    {'guid': 123, 'num': Decimal('5.00'), 'created_by': 'test'}

So on one box repr(decimal.Decimal('5.00')) results in 'Decimal("5.00")' on the other in "Decimal('5.00')". Is there any way to get arround the issue withyout creating more compliated test logic?

Answer 1

This is actually because the decimal module's source code has changed: In python 2.4 and python2.5 the decimal.Decimal.__repr__ function contains:

return 'Decimal("%s")' % str(self)

whereas in python2.6 it contains:

return "Decimal('%s')" % str(self)

So in this case the best thing to do is just to print out str() of the result and check the type separately if necessary...

Answer 2

Following the hits by David Fraser i found this suggestion by Raymond Hettinger on the Python mailinglist.

I now use something like this:

import sys
if sys.version_info[:2] <= (2, 5):
    # ugly monkeypatch to make doctests work. For the reasons see
    # See http://mail.python.org/pipermail/python-dev/2008-July/081420.html
    # It can go away once all our boxes run python > 2.5
    decimal.Decimal.__repr__ = lambda s: "Decimal('%s')" % str(s)