[Python-Dev] Finally fix installer to add Python to %PATH% on Windows

[Michael Foord]

On 28/01/2011 16:29, Brian Curtin wrote:
> On Fri, Jan 28, 2011 at 10:12, anatoly techtonik <techtonik at gmail.com 
> <mailto:techtonik at gmail.com>> wrote:
>
>     Hi, I'd like to
>
>     You probably know that after installation on Windows system it is
>     possible to call Python from Explorer's Run dialog (Win-R). It is
>     because Python path is added to App Paths registry key and Windows
>     Explorer shell checks this key when looking for executable.
>
>     But Python doesn't work from cmd session and, more importantly,
>     *Python doesn't work from .bat files*. It is because cmd shell doesn't
>     know about App Paths and relies on system PATH to find executable. As
>     far as I remember, there is no function in Python stdlib either, that
>     executes processes and does lookups in App Paths.
>
>     I never paid much attention to this fact, because I put several .bat
>     files for every 25, 26, 27, 31 and 32 version of Python into PATH
>     manually. But when bootstrap script for build environment of Native
>     Client (NaCl) said that I have no Python available and started to
>     install its own, I've asked myself - "How come? There are 5! possible
>     versions of Python on my system." It appeared that the following .bat
>     file doesn't work:
>
>     ---cut mypy.bat--
>     python.exe
>     ---cut mypy.bat--
>
>     C:\>mypy.bat
>
>     C:\>python.exe
>     'python.exe' is not recognized as an internal or external command,
>     operable program or batch file.
>
>
>     I've seen about 7 requests to add Python into %PATH% in installer. All
>     closed with no result, but with some fear and uncertainty. Martin
>     feared that MSI installers are not able to remove entry from PATH and
>     even if they can, they may kill the whole PATH instead of removing
>     just one entry.
>
>     To prove or dispel these fears, I've just installed/uninstalled
>     Mercurial from mercurial-1.7.3-1-x86.msi and App Engine from
>     GoogleAppEngine-1.4.1.msi several times. Both add entries to PATH and
>     both remove them without any further problems. Should we finally add
>     this to 3.2 installer for Python?
>
>     --
>     anatoly t.
>
>
> Definitely not for 3.2, but this is something I'd like to look into 
> for 3.3.
>
> Recently I've talked to two Python trainers/educators and the major 
> gripe their attendees see is that you can't just sit down and type 
> "python" and have something work. For multi-Python installs, we'll 
> have to define what that "something" is, but I think it should be 
> possible for the installer to optionally put Python into the path, and 
> to also remove itself on uninstall.
>

I've helped quite a few "python newbies" on Windows who are also 
surprised / frustrated on learning that "python" on the command line 
doesn't work after installing python.

All the best,

Michael Foord

> One of said trainers is running a course inside my company right now 
> and the training room VMs they are running on do not have the path 
> setup. Some users were puzzled as to why "python foo.py" doesn't work, 
> but executing "foo.py" does (via file association).
>
> One quick-and-dirty solution was to create a "Command Shell" shortcut 
> in the start menu which would just be a batch file that adds Python to 
> the path for that cmd session. It would be kind of similar to the 
> "Python (command line)" shortcut, which uses pythonw.exe. I think we 
> can do better than this, though.
>
>
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