Embedded python 2.6 interpreter can't "import sqlite3" on Windows XP

[Peter]

jdetaeye wrote:
> I am porting an application which embeds a Python interpreter to
> Python 2.6.
> On version 2.5 all is working fine, but importing the sqlite3 module
> doesn't work any more on 2.6.
> 
> The statement  "import sqlite3" does work fine when executed from in
> the python command prompt, ie not from the embedded interpreter.
> The same import gives the following error when executed from the
> embedded interpreter.
>    Python stacktrace:
>        Traceback (most recent call last):
>          File "<string>", line 2, in <module>
>          File "C:\Python26\lib\sqlite3\__init__.py", line 24, in
> <module>
>            from dbapi2 import *
>          File "C:\Python26\lib\sqlite3\dbapi2.py", line 27, in
> <module>
>            from _sqlite3 import *
>        ImportError: DLL load failed: A dynamic link library (DLL)
> initialization routine failed.
>    Windows popup window:
>        Runtime Error!
>        R6034
>        An application has made an attempt to load the C runtime
> library incorrectly.
>        Please contact the application's support team for more
> information.
> 
> Unfortunately the "application support team" (that is me :-) has no
> idea on how to move forward on this:
> a) I guess this is releated to the problem with manifest files,
> already reported in http://bugs.python.org/issue4120 ?
> b) What could be a solution or workaround for the problem?
> 
> All the above is on Windows XP.
> Other modules with have an extension DLL (such as ssl) give exactly
> the same problem.
> 
> All help appreciated,
> 
> Johan
> 

Python 2.6+ was built with Visual Studio 2008; therefore, the Microsoft 
Visual C++ 2008 Redistributable Package (run time libraries) must be 
installed on the computer that you are trying to run your python 
application.  If the computer already has Python 2.6+ installed "for all 
users", then the run time libraries should already be installed in 
c:\windows\winsxs.  On computers that do not have Python 2.6+ installed 
(or it was installed using "Install Just for Me"), you probably will 
need to install the Visual C++ 2008 Redistributable Package.  It is 
possible that some other application already installed the correct run 
time libraries in the c:\windows\winsxs directory.

Visual C++ 2008 Redistributable Package:
http://www.microsoft.com/downloads/details.aspx?FamilyID=9b2da534-3e03-4391-8a4d-074b9f2bc1bf&displaylang=en

After installing the Visual C++ 2008 Redistributable, you can find it 
under the c:\windows\winsxs directory.

Side-by-Side (sxs) Assemblies are Microsoft's answer to "DLL hell" and 
Visual C++ 2005 had them, too.  I believe the reason the Python 
community didn't see these problems earlier was that most computers 
already had the proper run time libraries installed.  See "Application 
Compatibility—Side-by-side Assemblies" in 
http://msdn.microsoft.com/en-us/magazine/cc302206.aspx and 
http://msdn.microsoft.com/en-us/magazine/ms997620.aspx for more 
information on Side-by-Side Assemblies.

Note that if future versions of Python are built with Visual Studio 2008 
with service pack (SP) #x and the build specifies that the SP #x updated 
run time libraries should be used, then you'll need to install the 
updated run time libraries.  See 
http://msdn.microsoft.com/en-us/library/cc664727.aspx and 
http://msdn.microsoft.com/en-us/library/ms235299(VS.80).aspx for more 
information on binding applications to specific run time libraries.

The following articles may also be of interest:

http://msdn.microsoft.com/en-us/library/ms235531.aspx
http://msdn.microsoft.com/en-us/library/ms235342.aspx
http://msdn.microsoft.com/en-us/library/aa374224.aspx

Of course everything I've just said may change with the next release of 
Python, because the Python maintainers are apparently looking at 
alternative ways around this issue.  Although I'm not a Microsoft fan, 
I'm not yet convinced that trying to work around Microsoft's winsxs 
requirements is a smart thing to do.

It might simplify things for python users and developers if the Python 
2.6+ installers always installed the VS C++ run time libraries into the 
winsxs directory.  Perhaps python tools that create embedded python 
applications could better document this issue, so that people using 
embedded applications will know that they have to install the proper run 
time libraries.  It's also possible that Microsoft will someday install 
these new Visual Studio 2008 run time libraries via their update service 
or a future service pack.

Peter