[Python-Dev] New Windows installer for Python 3.5

Steve Dower Steve.Dower at microsoft.com
Mon Jan 12 18:26:43 CET 2015

David Anthoff wrote:
>> I'll look into this, but it probably isn't going to work as part of
>> the installer. I have previously looked into being able to install arbitrary
>> side-by-side copies of Python, but that's near impossible as well.
>> Windows Installer doesn't really let you just copy files - it isn't
>> part of its intended functionality. It isn't too difficult to build custom
>> MSIs with certain parts of Python (such as the DLLs and the standard
>> library, but no docs, headers or EXEs) in a way that won't conflict with
>> other installs, but you're still using an MSI here which is not
>> necessarily ideal.
> Are administrative MSI installs an option, though? They don't register anything
> but just drop files, right? But see my comments below about a zip drop, which
> would be a much, much nicer option in my opinion.

Not to my knowledge. An administrative install puts the files in a shared location and allows users to run much faster installs that will then refer to that shared location rather than copying the files locally. As I said, MSI doesn't support plain file drops (often called "xcopy install" - you use that term later, but I'm not sure how well known it is).

>> We could release a ZIP file containing all the Python files.
> That would be absolutely FANTASTIC and would solve all problems around this
> topic. In theory we could handle this ourselves on our end, but this is for a
> small open source project and we are really hesitant to take on another software
> packaging job. Doing this right just for our product would be a fair amount of
> work, we would have to do this with every new Python release, we might mix
> things up etc., and really we are more interested in our piece of software than
> packaging Python ;) I think it would be a much nicer model if there was a zip to
> download from python.org.

Apart from the bit below, this would be identical to you installing Python once on your own machine and zipping up the files yourself. For the (considerably) less than 1% of Python users who want to do this, I don't think it's a big ask.

> There is another issue that keeps us from hosting our
> own files: we would have to figure out licensing issues, both related to python
> and to the msvcr*.dll and msvcp*.dll. I would feel much more comfortable if we
> didn't distribute python or other binaries, but just downloaded stuff from
> python.org as part of the setup process.

IANAL, but I've dealt with enough licensing issues in my day job that this makes me even more concerned about making a ZIP file available. If you're planning to do this, putting up a ZIP file could potentially expose Python (and presumably the PSF indirectly) to the liability that you should be taking on as a redistributor, if it's that important to your product. Without an actual legal opinion, I'm now -1 on making a ZIP download available for this purpose.

>> The only reason I hesitate on this is that it could cause significant
>> confusion for someone who doesn't really understand the implications,
>> while people like yourself who have thought about this are also capable
>> of finding workarounds and don't really need the ZIP file apart from
>> convenience.
> I was not clear in my previous email. I have NOT found a way to work around
> this. I have tried various hacks, but none really works. I got pretty far, but
> none really worked in all cases in a robust way. So I would certainly welcome a
> downloadable zip file a great deal. Is there maybe a compromise for now to have
> such a zip on the server, but not advertise it widely, and maybe put an
> "experimental"/"beta" moniker into the filename?

I gave you a workaround. Install Python just for yourself and zip up the install directory.

> I assume you would include the MS VC runtime files msvcr100.dll and msvcp100.dll
> in such a zip file?

Either that or redistribute them using the tools provided by Microsoft (there are redistributable merge modules and executable installers available). The advantage of the latter approach is that your users will automatically get the latest versions and security fixes.

> Is there any chance this might even be done (as an experimental version) for
> Python 3.4?

You'd have to ask Martin, so probably not. But the workaround I gave you will work for 3.4.

>> Making some of the fixes to
>> make python.exe more portable would relieve my concerns here.
> I see that. For our cases things seem to work, but I agree, it would be good if
> python.exe would try hard to work in a xcopy mode.
>>> The old MSI installer sort of had something like that with the MSI
>>> administrative install option. But it never really worked because
>>> the administrative install didn't drop the MSVC runtime dlls
>>> anywhere, as far as I could tell. At some point I hacked around that
>>> by modifying the MSI file in my setup program to also drop the MSVC
>>> runtime dlls, but
>>> that was VERY hacky...
>> I'm a little surprised that worked at all for what you were trying to do.
>> You'd be better off installing it once and then copying the files yourself.
> I got it to drop the msvcr100.dll, but haven't managed to get the msvcp100.dll
> out via an administrative install. The whole approach is a mess, I would MUCH
> prefer a zip file.
>> But overall, this is the sort of thing I do want to enable. I firmly
>> believe that Python from python.org is for *developers*, and those who
>> just want to run a Python application should be able to get a complete
>> package. This is very different from the *nix approach, but it makes far
>> more sense to Windows users. A good example is TortoiseHg, which bundles
>> everything so that users never even know they have Python 2.7 or
>> Mercurial installed on their machine. Making it easier for people to
>> bundle Python into their own applications is a good thing, as far as I'm
>> concerned.
> Yes, those are good examples. Right now doing this in the way these guys do is
> too much work for our small project... Anything that makes this easier would be
> appreciated.

I don't see how. All they've done is literally copy a Python installation into their install directory. Yes, they have their own launcher executables (py2exe generated, it looks like) and have precompiled the standard library and put it in a ZIP file, but you don't even need to go that far. Without knowing anything about your project I can't give specific suggestions, but simply dropping a Python installation in is not that difficult (and until the issues that Nick referred to are fixed, will have the same problems as TortoiseHg presumably has).

> Thanks! And the new installer looks great in general.



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