Allow types to be wrapped in functools.partial

[Former user]

(original reporter: ged) Currently (r5104), the following code:

from functools import partial
from sqlalchemy import *

metadata = MetaData('sqlite:///')

Unicode = partial(Unicode, assert_unicode=None)

thing_table = Table('thing', metadata,
    Column('name', Unicode, primary_key=True)
)

produce this traceback:

Traceback (most recent call last):
  File "test_partial.py", line 9, in <module>
    Column('name', Unicode, primary_key=True)
  File "/home/ged/devel/sqlalchemy/trunk/lib/sqlalchemy/schema.py", line 113, in __call__
    return type.__call__(self, name, metadata, *args, **kwargs)
  File "/home/ged/devel/sqlalchemy/trunk/lib/sqlalchemy/schema.py", line 246, in __init__
    self.__post_init(*args, **kwargs)
  File "/home/ged/devel/sqlalchemy/trunk/lib/sqlalchemy/schema.py", line 292, in __post_init
    self._init_items(*args)
  File "/home/ged/devel/sqlalchemy/trunk/lib/sqlalchemy/schema.py", line 54, in _init_items
    item._set_parent(self)
  File "/home/ged/devel/sqlalchemy/trunk/lib/sqlalchemy/schema.py", line 691, in _set_parent
    self._init_items(*toinit)
  File "/home/ged/devel/sqlalchemy/trunk/lib/sqlalchemy/schema.py", line 54, in _init_items
    item._set_parent(self)
AttributeError: 'functools.partial' object has no attribute '_set_parent'

This issue was initially reported at: http://elixir.ematia.de/trac/ticket/72

[Mike Bayer]

what happens if you just say:

Column('name', Unicode())

?

assuming a Unicode() instance is returned that should be fine.

[Former user]

Yes, that works. So should this trivial patch.

[Mike Bayer]

I was suggesting that you just call Unicode() in your own application code. That patch strikes me as extremely specific to an arbitrary use case. There's lots of ways to do partials in Python.

[Former user]

let to_instance handle any callable, not just types

[Former user]

There are other ways to do partial application, but partial is the standard. The use case is whenever there are several columns that need the same parameters.

However, I agree the solution isn't to add another special case. The above patch lets to_instance handle any callable by removing the current special treatment of types.

[Mike Bayer]

agreed on the use case to use partials, I meant the specific technique of using functools.partial. the new patch is much more agreeable, will try soon.

[Former user]

(original author: ged)

[Michael Trier]

Fixed in 56e88ed7c3b4bd6890087d6d2ced6514076d56c3

[Mike Bayer]

Removing milestone: 0.5.0 (automated comment)