Parser variations

[Bruce Eckel]

I just had an experience I thought I'd share to prevent others from the same bug.

I have a Windows 7 desktop and a MacBook. I've done most of the development on the Win7 machine, but I'm traveling so switched to the MacBook. I've done a lot to isolate the differences between the two, but when I switched over to the MacBook I discovered that I'd get to a phase of processing where most of my document just vanished. I attributed this to Mac/Win differences and tried to figure it out that way but after sleeping on it realized that I hadn't installed lxml on the MacBook so the system was quietly falling back to a different parser, and the behavior between parsers was so different that I was getting completely different results.

Fixed it by specifying "lxml" as the second BeautifulSoup constructor argument, so now when my system tries to build without lxml it puts out an appropriate error message.

The parser fallback behavior sounds like a good idea at first but since the behavior is so different I highly recommend specifying whatever parser you're using via the constructor, so if you move your program to a machine that doesn't have it you get a hint about what's wring.

-- Bruce Eckel
www.Reinventing-Business.com
www.MindviewInc.com