Hi, John. I'm maintainer of PyMySQL. I'm sorry about bug of PyMySQL. But the bug is completely unrelated to Python 3. You may encounter the bug on Python 2 too.
I've already made mysqlclient, the fork of MySQLdb supporting Python 3. On Sat, Mar 14, 2015 at 6:08 AM, John Nagle <na...@animats.com> wrote: > I'm approaching the end of converting a large system from Python 2 to > Python 3. Here's why you don't want to do this. > > The language changes aren't that bad, and they're known and > documented. It's the package changes that are the problem. > Discovering and fixing all the new bugs takes a while. > > > BeautifulSoup: > > BeautifulSoup 3 has been phased out. I had my own version of > BeautifulSoup 3, modified for greater robustness. But that was > years ago. So I converted to BeautifulSoup 4, as the documentation > says to do. > > The HTML5parser module is claimed to parse as a browser does, with > all the error tolerance specified in the HTML5 spec. (The spec > actually specifies how to handle bad HTML consistently across > browsers in great detail, and HTML5parser has code in it for that.) > > It doesn't deliver on that promise, though. Some sites crash > BeautifulSoup 4/HTML5parser. Try "kroger.com", which has HTML with > <head><head>. The parse tree constructed has a bad link, > and trying to use the parse tree results in exceptions. > Submitted bug report. Appears to be another case of > a known bug. No workaround at this time. > > https://bugs.launchpad.net/beautifulsoup/+bug/1270611 > https://bugs.launchpad.net/beautifulsoup/+bug/1430633 > > > PyMySQL: > > "Pymysql is a pure Python drop-in replacement for MySQLdb". > Sounds good. Then I discover that LOAD DATA LOCAL wasn't > implemented in the version on PyPi. It's on Github, though, > and I got the authors to push that out to PyPi. It > works on test cases. But it doesn't work on a big job, > because the default size of MySQL packets was set to 16MB. > This made the LOAD DATA LOCAL code try to send the entire > file being loaded as one giant MySQL packet. Unless you > configure the MySQL server with 16MB buffers, this fails, with > an obscure "server has gone away" message. Found the > problem, came up with a workaround, submitted a bug report, > and it's being fixed. > > https://github.com/PyMySQL/PyMySQL/issues/317 > > > SSL: > > All the new TLS/SSL support is in Python 3. That's good. > Unfortunately, using Firefox's set of SSL certs, some > important sites (such as "verisign.com") don't validate. > This turned out to be a complex problem involving Verisign > cross-signing a certificate, which created a certificate > hierarchy that some versions of OpenSSL can't handle. > There's now a version of OpenSSL that can handle it, but > the Python library has to make a call to use it, and > that's going in but isn't deployed yet. This bug > resulted in much finger-pointing between the Python > and OpenSSL developers, the Mozilla certificate store > maintainers, and Verisign. It's now been sorted out, > but not all the fixes are deployed. Because "ssl" is > a core Python module, this will remain broken until the > next Python release, on both the 2.7 and 3.4 lines. > > Also, for no particularly good reason, the exception > "SSL.CertificateError" is not a subclass of "SSL.Error", > resulting in a routine exception not being recognized. > > Bug reports submitted for both OpenSSL and Python SSL. > Much discussion. Problem fixed, but fix is in next > version of Python. No workaround at this time. > > http://bugs.python.org/issue23476 > > > Pickle: > > As I just posted recently, CPickle on Python 3.4 seems to > have a memory corruption bug. Pure-Python Pickle is fine. > So a workaround is possible. Bug report submitted. > > http://bugs.python.org/issue23655 > > > Converting a large application program to Python 3 > thus required diagnosing four library bugs and filing > bug reports on all of them. Workarounds are known > for two of the problems. I can't deploy the Python 3 > version on the servers yet. > > John Nagle > -- > https://mail.python.org/mailman/listinfo/python-list -- INADA Naoki <songofaca...@gmail.com> -- https://mail.python.org/mailman/listinfo/python-list
