python/xpath question..

morning....

i apologize up front as this is really more of an xpath question..

in my python, i'm using the xpath function to iterate/parse some html. i can
do something like

s=d.xpath("//tr/td/text()")
count=len(s)

and get the number of nodes that have text

i can then do something like
s=d.xpath("//tr/td")
count2=len(s)

and get the number of total nodes...
by subtracting, i can get the number of nodes, without text.. is there an
easier way??!!
count2-count

ie, if i have something like
<tr>
<td></td>
<td>foo</td>
</tr>

is there a way to get the count that there is a single "td" node with
text()=""

thanks


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