Re: 'bzr init-repo .' crashes for lack of module bz2. Help, please!

[Alan Mackenzie <acm@muc.de>]

Hi, David,

On Thu, Dec 31, 2009 at 05:04:41PM +0000, David De La Harpe Golden wrote:
> Alan Mackenzie wrote:

> >I was lacking this file [bzlib.h], so I downloaded and built the
> >latest version of bzip2. 

> And rebuild python against this version, right, with "bz2" absent from
> the list of modules that failed to build this time due to failure to 
> "find the necessary bits"? Does the "python" to
> get a python repl then "import bz2" test succeed now?

That's what I did, and no "import bz2" didn't succeed.  However, it did
once I'd remembered to do "make install" on the newly build Python.

[ .... ]

> >I still get the same error message, which I don't understand,
> >namely:

> >    bzr: ERROR: exceptions.ImportError: failed to load
> >    bzrlib.repofmt.groupcompress_repo.RepositoryFormat2a: No module
> >    named bz2

> >Presumably "bzrlib.repofmt.groupcompress_repo" means the file
> >.../bzrlib/repofmt/groupcompress_repo.py, but what, exactly, is a "module
> >named bz2"? 

> In this case, it means a python extension "module" being a python 
> binding to libbz2 (*).  Such extensions are atypical python modules 
> implemented as C libs rather than python. The C code uses the python C 
> implementation's ("cpython") C API to act like a python module to python 
> code running under that implementation, providing additional 
> python-callable functions and python-usable data types.  It's actually a 
> pretty typical way of extending scripting languages implemented in C, 
> though python has now also introduced the more Lisp-conventional "FFI" 
> approach for such things in module "ctypes" (just mentioning for 
> completeness).
> http://docs.python.org/extending/index.html
> http://docs.python.org/library/ctypes.html

Thanks for this explanation.

I've now got bzip2, Python and bzr installed and talking to each other,
such that I can carry on with the BzrForEmacsDevs on the Emacs wiki.
Thanks!

-- 
Alan Mackenzie (Nuremberg, Germany).