[Python-Dev] Existence of pythonNN.zip in sys.path

[Eric V. Smith]

On 5/6/2014 1:14 PM, Terry Reedy wrote:
> On 5/5/2014 5:32 PM, Anthony Tuininga wrote:
>> Hi,
>>
>> I am the author of cx_Freeze which creates "frozen" executables from
>> Python scripts. To this point I have been using frozen modules (compiled
>> C) but this has the side effect of bundling parts of Python with a
>> cx_Freeze release -- and this has bitten me on a number of occasions
>> when newer versions of Python use slightly incompatible modules. :-)
>>
>> By scanning the code I discovered that Python automatically searches on
>> startup
>>
>> <PYTHONHOME>/lib/pythonNN.zip
>>
>> where NN is replaced by the major and minor version that is being
>> executed. Using this would allow me to ensure that bootstrap modules are
>> not bundled with cx_Freeze but acquired from the distribution that is
>> actually using it -- thereby eliminating the hassle noted above.
>>
>> I have tested this approach and found it works flawlessly. There is,
>> however, no documentation that I can find for the contents of sys.path
>> -- the documentation simply says that it is an installation default and
>> doesn't specify what that default is.
>>
>> So my question is: can I safely make use of this "feature"? It has
>> remained in place since at least Python 2.6 but I don't want to assume
>> anything. Please advise! Thanks.
> 
> I would say yes. AFAIK /lib has always by used for the stdlib on Windows
> and /lib/pythonxy on *nix. Both are mentioned in the 4th paragraph of
> the site module doc. We do not lightly change directory structure. PEP
> 273 then says "The zip archive must be treated exactly as a subdirectory
> tree,". I take this to mean that lib/pythonxy.zip should work the same
> as lib/pythonxy/ does.
> 
> You can depend on the feature working as long as it works. Your bigger
> worry is accidental regression. I suggest testing release candidates
> (there is one for 3.4.1 now, I believe) and also an early alpha and beta
> for new release. The candidate may have a zip patch affecting central
> directory reading. If not, there is an issue on the tracker. You could
> monitor patches by filtering the new-issue announcements for 'zip'.

The best course of action would be to integrate any such tests into the
stdlib test suite, where a regression would immediately be detected.

Eric.