[Python-Dev] Re: [Patches] [Patch #101234] Allow all assignment expressions after 'import something as' (original) (raw)

Thomas Wouters thomas@xs4all.net
Sun, 20 Aug 2000 22:49:18 +0200

On Sun, Aug 20, 2000 at 01:02:32PM -0700, noreply@sourceforge.net wrote:

Summary: Allow all assignment expressions after 'import something as'

Date: 2000-Aug-19 21:29 By: twouters

Comment: This absurdly simple patch (4 lines changed in 2 files) turns 'import-as' and 'from-import-as' into true assignment expressions: the name given after 'as' can be any expression that is a valid l-value:

>>> from sys import versioninfo as (maj,min,pl,relnam,relno) >>> maj,min,pl,relnam,relno (2, 0, 0, 'beta', 1)

[snip other examples]

This looks so natural, I would almost treat this as a bugfix instead of a new feature ;)

-------------------------------------------------------

Date: 2000-Aug-20 20:02 By: nowonder Comment: Looks fine. Works as I expect. Doesn't break old code. I hope Guido likes it (assigned to gvanrossum).

Actually, it will break old code. Try using some of those tricks on, say, 'encodings', like so (excessively convoluted to prove a point ;):

x = {} from encodings import cp1006 as x[oct(1)], cp1026 as x[hex(20)] Traceback (most recent call last): File "", line 1, in ? ImportError: cannot import name cp1026

I've another patch waiting which I'll upload after some cleanup, which circumvents this. The problem is that find_from_args is having a hard time figuring out how 'import' is being called, exactly. So instead, I create a list before calling import, straight from the information available at compile-time. (It's only a list because it is currently a list, I would prefer to make it a tuple instead but I donno if it would break stuff)

That patch is necessary to be able to support this new behaviour, but I think it's worth checking in even if this patch is rejected -- it speeds up pystone ! :-) Basically it moves the logic of finding out what the import arguments are to com_import_stmt() (at compiletime), rather than the 'IMPORT_NAME' bytecode (at runtime).

The only downside is that it adds all 'from-import' arguments to the co_consts list (as PyString objects) as well as where they already are, the co_names list (as normal strings). I don't think that's a high price to pay, myself, and mayhaps the actual storage use could be reduced by making the one point to the data of the other. Not sure if it's worth it, though.

I've just uploaded the other patch, it can be found here: http://sourceforge.net/patch/?func=detailpatch&patch_id=101243&group_id=5470

-- Thomas Wouters <thomas@xs4all.net>

Hi! I'm a .signature virus! copy me into your .signature file to help me spread!