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Hi, I'm Paul Carvill and I'm a web developer. I am Head of Interface Development at LBi, Europe's largest digital agency.

I also like walking, cooking, Bollywood and rock 'n' roll.

Archive for the ‘Python’ Category

How to handle a Python BadKeyError exception in Google AppEngine

Tuesday, June 1st, 2010

This drove me nuts an hour tonight. If you’re trying to get an entity key using something like:

yourKey = someString
candidate = Candidate( key=db.Key(yourKey) )

and you get a BadKeyError, it’s because the string you’re sending in isn’t the right length. Also, AppEngine doesn’t return None from the Key method but instead returns a BadKeyError exception. You can handle this by doing:

yourKey = someString
try:
   candidate = Candidate( key=db.Key(yourKey) )
except db.BadKeyError:
   # handle the exception here

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Posted in Development, Python, Work | Comments Off

Using Python with MySQL on Mac OSX 10.5 Leopard

Wednesday, March 18th, 2009

If you try to build the MySQL Python library on Mac OS X 10.5 (Leopard) you’ll get an error similar to this:

/usr/include/sys/types.h:92: error: duplicate ‘unsigned’
/usr/include/sys/types.h:92: error: two or more data types in declaration specifiers
error: command 'gcc' failed with exit status 1

I found the fix for this error here: http://www.keningle.com/?p=11, via a comment on this site: http://dotnet.org.za/ncode/archive/2007/01/31/setting-up-mysql-for-python-mysqldb-on-mac-os-x-2.aspx. It’s just a couple of lines in Terminal, adding a symlink so the library knows where to look to find the files.

Some background: Unless you’re using SQLite, you need to install a Python library to interface with your chosen database (PostgreSQL, MySQL or Oracle).

The MySQL library can be downloaded here: http://www.djangoproject.com/r/python-mysql/

But it seems there are a few problems running this library on Mac OS X 10.5 (Leopard), hence the above fix.

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Posted in Development, Python | Comments Off