FazBrowse GitHub Viewer | Trending |
URL:
| Home
Tools: [Download Repo ZIP]   [Original HTTPS Page]

[3.10] Minor edits to the Descriptor HowTo Guide (GH-24901) by miss-islington · Pull Request #98114 · python/cpython · GitHub

/ cpython Public

[3.10] Minor edits to the Descriptor HowTo Guide (GH-24901) #98114

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
rhettinger merged 1 commit into from
Oct 9, 2022
Conversation 0 Commits 1 Checks 0 Files changed
Merged

[3.10] Minor edits to the Descriptor HowTo Guide (GH-24901) #98114

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension .rst  (1) All 1 file type selected
Viewed files
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Unified
Split
Hide whitespace
Diff view
Unified
Split
Hide whitespace
14 changes: 8 additions & 6 deletions Doc/howto/descriptor.rst
Show comments
View file
Open in desktop
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
Show hidden characters
Original file line number Diff line number Diff line change
Expand Up @@ -847,7 +847,7 @@ afterwards, :meth:`__set_name__` will need to be called manually.
ORM example
-----------

The following code is simplified skeleton showing how data descriptors could
The following code is a simplified skeleton showing how data descriptors could
be used to implement an `object relational mapping
<https://en.wikipedia.org/wiki/Object%E2%80%93relational_mapping>`_.

Expand Down Expand Up @@ -1533,6 +1533,8 @@ by member descriptors:
def __get__(self, obj, objtype=None):
'Emulate member_get() in Objects/descrobject.c'
# Also see PyMember_GetOne() in Python/structmember.c
if obj is None:
return self
value = obj._slotvalues[self.offset]
if value is null:
raise AttributeError(self.name)
Expand Down Expand Up @@ -1561,13 +1563,13 @@ variables:
class Type(type):
'Simulate how the type metaclass adds member objects for slots'

def __new__(mcls, clsname, bases, mapping):
def __new__(mcls, clsname, bases, mapping, **kwargs):
'Emulate type_new() in Objects/typeobject.c'
# type_new() calls PyTypeReady() which calls add_methods()
slot_names = mapping.get('slot_names', [])
for offset, name in enumerate(slot_names):
mapping[name] = Member(name, clsname, offset)
return type.__new__(mcls, clsname, bases, mapping)
return type.__new__(mcls, clsname, bases, mapping, **kwargs)

The :meth:`object.__new__` method takes care of creating instances that have
slots instead of an instance dictionary. Here is a rough simulation in pure
Expand All @@ -1578,7 +1580,7 @@ Python:
class Object:
'Simulate how object.__new__() allocates memory for __slots__'

def __new__(cls, *args):
def __new__(cls, *args, **kwargs):
'Emulate object_new() in Objects/typeobject.c'
inst = super().__new__(cls)
if hasattr(cls, 'slot_names'):
Expand All @@ -1591,7 +1593,7 @@ Python:
cls = type(self)
if hasattr(cls, 'slot_names') and name not in cls.slot_names:
raise AttributeError(
f'{type(self).__name__!r} object has no attribute {name!r}'
f'{cls.__name__!r} object has no attribute {name!r}'
)
super().__setattr__(name, value)

Expand All @@ -1600,7 +1602,7 @@ Python:
cls = type(self)
if hasattr(cls, 'slot_names') and name not in cls.slot_names:
raise AttributeError(
f'{type(self).__name__!r} object has no attribute {name!r}'
f'{cls.__name__!r} object has no attribute {name!r}'
)
super().__delattr__(name)

Expand Down
Back | FazBrowse Home | New Git URL