Re: [XEN PATCH v1] tools/python: Add python3 compatibility

[Javi Merino <javi.merino@xxxxxxxxx>]

On Tue, Oct 10, 2023 at 05:27:03PM +0200, Marek Marczykowski-Górecki wrote:
> On Tue, Oct 10, 2023 at 03:18:45PM +0100, Javi Merino wrote:
> > Most of the work for python3 compatibility was done in
> > 1430c5a8cad4 (tools/python: Python 3 compatibility, 2019-12-18).  This
> > just adds a few builtins needed for python3.
> > 
> > Resolves: xen-project/xen#156
> > 
> > Signed-off-by: Javi Merino <javi.merino@xxxxxxxxx>
> > ---
> > 
> > I haven't tested it.
> > 
> >  README                                     | 1 +
> >  tools/python/scripts/convert-legacy-stream | 3 +++
> >  2 files changed, 4 insertions(+)
> > 
> > diff --git a/README b/README
> > index 855db01d36..44ed88c392 100644
> > --- a/README
> > +++ b/README
> > @@ -51,6 +51,7 @@ provided by your OS distributor:
> >      * POSIX compatible awk
> >      * Development install of zlib (e.g., zlib-dev)
> >      * Development install of Python 2.7 or later (e.g., python-dev)
> > +      - If using Python 2.7, you also need the future module.  This is not 
> > needed for Python 3.
> >      * Development install of curses (e.g., libncurses-dev)
> >      * Development install of openssl (e.g., openssl-dev)
> >      * Development install of x11 (e.g. xorg-x11-dev)
> > diff --git a/tools/python/scripts/convert-legacy-stream 
> > b/tools/python/scripts/convert-legacy-stream
> > index 7fe375a668..26a66c50fc 100755
> > --- a/tools/python/scripts/convert-legacy-stream
> > +++ b/tools/python/scripts/convert-legacy-stream
> > @@ -8,6 +8,9 @@ Convert a legacy migration stream to a v2 stream.
> >  from __future__ import print_function
> >  from __future__ import division
> >  
> > +from builtins import zip
> > +from builtins import range
> > +from builtins import object
> 
> In which python version it's needed? The thing about builtins is they
> are available without explicit import.

In python3, this change is a noop.  In python2, this change makes zip,
range and object be consistent with its python3 counterparts:

- zip: with the change, zip returns an iterator in python2,
  like it does in python3.  It's equivalent to izip from itertools or
  `from future_builtins import zip`[0]

- range: with the change, in python2 range behaves like xrange() used
  to. It returns an object instead of returning the list.[1]

- object: with the change, in python2 the string representation of
  VM() is in unicode, as it is for python3.

[0] 
https://stackless.readthedocs.io/en/2.7-slp/library/future_builtins.html#future_builtins.zip
[1] https://docs.python.org/3/library/stdtypes.html#ranges

Cheers,
Javi