Currently there is no way to get the default scheme for *current* platform other than plainly *assuming* that that is os.name unless it is posix, in which case it becomes posix_prefix. 

PyPM needs to know this. But I am slightly reluctant to hardcode it. I would rather use the _get_default_scheme() .. but only if it is known to be maintained for backward compat.

Thoughts?

Ideally I like to have a function like this:

            def get_current_scheme(usersite=False):
                scheme = os.name
                if usersite:
                    scheme += '_user'
                elif scheme == 'posix':
                    scheme = 'posix_prefix'

This would make it very easy to find the scheme for current Python installation - be it the global site-packages, or virtualenv or user site directory.

Though, generally it can take into consideration other "sub schemes" as well - prefix, home and user:


             def get_current_scheme(subscheme=oneof('default', 'home', 'user')):

Its a good idea to have that API. 

Now for the subscheme, 


   def get_current_scheme(subscheme=oneof('default', 'home', 'user')):

This doesn't work because the installed Python has already chosen a scheme between default or home.

So I'd rather have two APIs answering to that:

- get_current_scheme() : what's the default scheme for this python installation ?
- get_current_user_scheme() :  what's the default user scheme for his python installation

Next, if you want to browse the various available schemes for the platform, we could change "get_scheme_names()" and add a new parameter, saying that we want only the scheme for the current OS:

  get_scheme_names(current_platform=False)



(removing 2.7 as a target -- it's too late)

On 2010-05-20, at 2:45 AM, Tarek Ziadé wrote:

> So I'd rather have two APIs answering to that:
> 
> - get_current_scheme() : what's the default scheme for this python installation ?
> - get_current_user_scheme() :  what's the default user scheme for his python installation

+1

> Next, if you want to browse the various available schemes for the platform, we could change "get_scheme_names()" and add a new parameter, saying that we want only the scheme for the current OS:
> 
>  get_scheme_names(current_platform=False)

+1 as well. Perhaps `get_scheme_names(all=True)`? This seems like it can be done for 2.7, if found to be worthy of implementation.

> removing 2.7 as a target -- it's too late

If contribute a patch to `get_current_scheme` and `get_current_user_scheme`, will be accepted as part of 2.7?

Roughly I would do something like this:

            scheme = os.name
            if usersite: # get_current_user_scheme
                if sys.platform == 'darwin':
                    scheme = 'osx_framework_user'
                else:
                    scheme += '_user'
            elif scheme == 'posix':
                scheme = 'posix_prefix'
            return scheme

Here it is:

        def get_current_scheme():
            scheme = os.name
            if scheme == 'posix':
                scheme = 'posix_prefix'
            return scheme

        def get_current_user_scheme():
            scheme = os.name
            if sys.platform == 'darwin':
                scheme = 'osx_framework_user'
            else:
                scheme += '_user'
            return scheme

What do you think?

No sorry, no API change for 2.7 at this point. We are in beta stage.

Now for the implementation, it's going to be a little more complex. We need to look at variables like PYTHONFRAMEWORK for instance.

I wonder if the scheme names could be made more consistent, removing the need for a function.