warnings filters for varying message

[John Reid]

Looking at the docs for warnings.simplefilter
(http://docs.python.org/2/library/warnings.html) I think the following
script should only produce one warning at each line as any message is
matched by the simple filter

import warnings
warnings.simplefilter('default')
for i in xrange(2):
    warnings.warn('Warning message') # This prints 1 warning
    warnings.warn("Warning %d" % i)  # This prints 2 warnings

What do I need to do to get the warnings module just to print one
warning for the second warnings.warn line?

Thanks,
John.