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authorVictor Stinner <victor.stinner@gmail.com>2016-12-19 12:12:08 (GMT)
committerVictor Stinner <victor.stinner@gmail.com>2016-12-19 12:12:08 (GMT)
commitb6522d0f77297cca197e724dda06814568604a93 (patch)
treedc050d53f9dfd78b389f80909873df04693ee700
parentaf324157c672427f6a47b9698de8ab20d2dcb6a9 (diff)
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abstract.h: remove long outdated comment
Issue #28838: The documentation is of the Python C API is more complete and more up to date than this old comment. Removal suggested by Antoine Pitrou.
-rw-r--r--Include/abstract.h120
1 files changed, 2 insertions, 118 deletions
diff --git a/Include/abstract.h b/Include/abstract.h
index f6dfc67..cfd240c 100644
--- a/Include/abstract.h
+++ b/Include/abstract.h
@@ -1,127 +1,11 @@
+/* Abstract Object Interface (many thanks to Jim Fulton) */
+
#ifndef Py_ABSTRACTOBJECT_H
#define Py_ABSTRACTOBJECT_H
#ifdef __cplusplus
extern "C" {
#endif
-/* Abstract Object Interface (many thanks to Jim Fulton) */
-
-/*
- PROPOSAL: A Generic Python Object Interface for Python C Modules
-
-Problem
-
- Python modules written in C that must access Python objects must do
- so through routines whose interfaces are described by a set of
- include files. Unfortunately, these routines vary according to the
- object accessed. To use these routines, the C programmer must check
- the type of the object being used and must call a routine based on
- the object type. For example, to access an element of a sequence,
- the programmer must determine whether the sequence is a list or a
- tuple:
-
- if (is_tupleobject(o))
- e = gettupleitem(o, i)
- else if (is_listitem(o))
- e = getlistitem(o, i)
-
- If the programmer wants to get an item from another type of object
- that provides sequence behavior, there is no clear way to do it
- correctly.
-
- The persistent programmer may peruse object.h and find that the
- _typeobject structure provides a means of invoking up to (currently
- about) 41 special operators. So, for example, a routine can get an
- item from any object that provides sequence behavior. However, to
- use this mechanism, the programmer must make their code dependent on
- the current Python implementation.
-
- Also, certain semantics, especially memory management semantics, may
- differ by the type of object being used. Unfortunately, these
- semantics are not clearly described in the current include files.
- An abstract interface providing more consistent semantics is needed.
-
-Proposal
-
- I propose the creation of a standard interface (with an associated
- library of routines and/or macros) for generically obtaining the
- services of Python objects. This proposal can be viewed as one
- components of a Python C interface consisting of several components.
-
- From the viewpoint of C access to Python services, we have (as
- suggested by Guido in off-line discussions):
-
- - "Very high level layer": two or three functions that let you exec or
- eval arbitrary Python code given as a string in a module whose name is
- given, passing C values in and getting C values out using
- mkvalue/getargs style format strings. This does not require the user
- to declare any variables of type "PyObject *". This should be enough
- to write a simple application that gets Python code from the user,
- execs it, and returns the output or errors. (Error handling must also
- be part of this API.)
-
- - "Abstract objects layer": which is the subject of this proposal.
- It has many functions operating on objects, and lest you do many
- things from C that you can also write in Python, without going
- through the Python parser.
-
- - "Concrete objects layer": This is the public type-dependent
- interface provided by the standard built-in types, such as floats,
- strings, and lists. This interface exists and is currently
- documented by the collection of include files provided with the
- Python distributions.
-
- From the point of view of Python accessing services provided by C
- modules:
-
- - "Python module interface": this interface consist of the basic
- routines used to define modules and their members. Most of the
- current extensions-writing guide deals with this interface.
-
- - "Built-in object interface": this is the interface that a new
- built-in type must provide and the mechanisms and rules that a
- developer of a new built-in type must use and follow.
-
- This proposal is a "first-cut" that is intended to spur
- discussion. See especially the lists of notes.
-
- The Python C object interface will provide four protocols: object,
- numeric, sequence, and mapping. Each protocol consists of a
- collection of related operations. If an operation that is not
- provided by a particular type is invoked, then a standard exception,
- NotImplementedError is raised with an operation name as an argument.
- In addition, for convenience this interface defines a set of
- constructors for building objects of built-in types. This is needed
- so new objects can be returned from C functions that otherwise treat
- objects generically.
-
-Memory Management
-
- For all of the functions described in this proposal, if a function
- retains a reference to a Python object passed as an argument, then the
- function will increase the reference count of the object. It is
- unnecessary for the caller to increase the reference count of an
- argument in anticipation of the object's retention.
-
- All Python objects returned from functions should be treated as new
- objects. Functions that return objects assume that the caller will
- retain a reference and the reference count of the object has already
- been incremented to account for this fact. A caller that does not
- retain a reference to an object that is returned from a function
- must decrement the reference count of the object (using
- DECREF(object)) to prevent memory leaks.
-
- Note that the behavior mentioned here is different from the current
- behavior for some objects (e.g. lists and tuples) when certain
- type-specific routines are called directly (e.g. setlistitem). The
- proposed abstraction layer will provide a consistent memory
- management interface, correcting for inconsistent behavior for some
- built-in types.
-
-Protocols
-*/
-
-
/* === Object Protocol ================================================== */
/* Implemented elsewhere: