I'm trying to select all the tables inside a division which has xpath similar to //*[@id="mw-content-text"]/table[@class="wikitable sortable jquery-tablesorter"]. But the selector doesn't returns any value. How can I get through those tags which have spaces in their id/class ?
I had the same issue because I was trying to scrape a wikipedia page. The class name for the table shows up as "wikitable sortable jquery-tablesorter" because of the plugin mentioned in the other answer which adds to the class name after it is used. 
In order to pick up the table you can just look for the following class instead "wikitable sortable". This picks up the code for me.
How to select tables in scrapy using selectors whose class id have spaces in it?