#ifndef Py_ABSTRACTOBJECT_H #define Py_ABSTRACTOBJECT_H #ifdef __cplusplus extern "C" { #endif /*********************************************************** Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam, The Netherlands. All Rights Reserved Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation, and that the names of Stichting Mathematisch Centrum or CWI not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. ******************************************************************/ /* 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 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 provides 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 a 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 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx*/ /* Object Protocol: */ /* Implemented elsewhere: int PyObject_Print(PyObject *o, FILE *fp, int flags); Print an object, o, on file, fp. Returns -1 on error. The flags argument is used to enable certain printing options. The only option currently supported is Py_Print_RAW. (What should be said about Py_Print_RAW?) */ /* Implemented elsewhere: int PyObject_HasAttrString(PyObject *o, char *attr_name); Returns 1 if o has the attribute attr_name, and 0 otherwise. This is equivalent to the Python expression: hasattr(o,attr_name). This function always succeeds. */ /* Implemented elsewhere: PyObject* PyObject_GetAttrString(PyObject *o, char *attr_name); Retrieve an attributed named attr_name form object o. Returns the attribute value on success, or NULL on failure. This is the equivalent of the Python expression: o.attr_name. */ /* Implemented elsewhere: int PyObject_HasAttr(PyObject *o, PyObject *attr_name); Returns 1 if o has the attribute attr_name, and 0 otherwise. This is equivalent to the Python expression: hasattr(o,attr_name). This function always succeeds. */ /* Implemented elsewhere: PyObject* PyObject_GetAttr(PyObject *o, PyObject *attr_name); Retrieve an attributed named attr_name form object o. Returns the attribute value on success, or NULL on failure. This is the equivalent of the Python expression: o.attr_name. */ /* Implemented elsewhere: int PyObject_SetAttrString(PyObject *o, char *attr_name, PyObject *v); Set the value of the attribute named attr_name, for object o, to the value, v. Returns -1 on failure. This is the equivalent of the Python statement: o.attr_name=v. */ /* Implemented elsewhere: int PyObject_SetAttr(PyObject *o, PyObject *attr_name, PyObject *v); Set the value of the attribute named attr_name, for object o, to the value, v. Returns -1 on failure. This is the equivalent of the Python statement: o.attr_name=v. */ /* implemented as a macro: int PyObject_DelAttrString(PyObject *o, char *attr_name); Delete attribute named attr_name, for object o. Returns -1 on failure. This is the equivalent of the Python statement: del o.attr_name. */ #define PyObject_DelAttrString(O,A) PyObject_SetAttrString((O),(A),NULL) /* implemented as a macro: int PyObject_DelAttr(PyObject *o, PyObject *attr_name); Delete attribute named attr_name, for object o. Returns -1 on failure. This is the equivalent of the Python statement: del o.attr_name. */ #define PyObject_DelAttr(O,A) PyObject_SetAttr((O),(A),NULL) int PyObject_Cmp Py_PROTO((PyObject *o1, PyObject *o2, int *result)); /* Compare the values of o1 and o2 using a routine provided by o1, if one exists, otherwise with a routine provided by o2. The result of the comparison is returned in result. Returns -1 on failure. This is the equivalent of the Python statement: result=cmp(o1,o2). */ /* Implemented elsewhere: int PyObject_Compare(PyObject *o1, PyObject *o2); Compare the values of o1 and o2 using a routine provided by o1, if one exists, otherwise with a routine provided by o2. Returns the result of the comparison on success. On error, the value returned is undefined. This is equivalent to the Python expression: cmp(o1,o2). */ /* Implemented elsewhere: PyObject *PyObject_Repr(PyObject *o); Compute the string representation of object, o. Returns the string representation on success, NULL on failure. This is the equivalent of the Python expression: repr(o). Called by the repr() built-in function and by reverse quotes. */ /* Implemented elsewhere: PyObject *PyObject_Str(PyObject *o); Compute the string representation of object, o. Returns the string representation on success, NULL on failure. This is the equivalent of the Python expression: str(o).) Called by the str() built-in function and by the print statement. */ int PyCallable_Check Py_PROTO((PyObject *o)); /* Determine if the object, o, is callable. Return 1 if the object is callable and 0 otherwise. This function always succeeds. */ PyObject *PyObject_CallObject Py_PROTO((PyObject *callable_object, PyObject *args)); /* Call a callable Python object, callable_object, with arguments given by the tuple, args. If no arguments are needed, then args may be NULL. Returns the result of the call on success, or NULL on failure. This is the equivalent of the Python expression: apply(o,args). */ PyObject *PyObject_CallFunction Py_PROTO((PyObject *callable_object, char *format, ...)); /* Call a callable Python object, callable_object, with a variable number of C arguments. The C arguments are described using a mkvalue-style format string. The format may be NULL, indicating that no arguments are provided. Returns the result of the call on success, or NULL on failure. This is the equivalent of the Python expression: apply(o,args). */ PyObject *PyObject_CallMethod Py_PROTO((PyObject *o, char *m, char *format, ...)); /* Call the method named m of object o with a variable number of C arguments. The C arguments are described by a mkvalue format string. The format may be NULL, indicating that no arguments are provided. Returns the result of the call on success, or NULL on failure. This is the equivalent of the Python expression: o.method(args). Note that Special method names, such as "__add__", "__getitem__", and so on are not supported. The specific abstract-object routines for these must be used. */ /* Implemented elsewhere: long PyObject_Hash(PyObject *o); Compute and return the hash, hash_value, of an object, o. On failure, return -1. This is the equivalent of the Python expression: hash(o). */ /* Implemented elsewhere: int PyObject_IsTrue(PyObject *o); Returns 1 if the object, o, is considered to be true, and 0 otherwise. This is equivalent to the Python expression: not not o This function always succeeds. */ PyObject *PyObject_Type Py_PROTO((PyObject *o)); /* On success, returns a type object corresponding to the object type of object o. On failure, returns NULL. This is equivalent to the Python expression: type(o). */ int PyObject_Length Py_PROTO((PyObject *o)); /* Return the length of object o. If the object, o, provides both sequence and mapping protocols, the sequence length is returned. On error, -1 is returned. This is the equivalent to the Python expression: len(o). */ PyObject *PyObject_GetItem Py_PROTO((PyObject *o, PyObject *key)); /* Return element of o corresponding to the object, key, or NULL on failure. This is the equivalent of the Python expression: o[key]. */ int PyObject_SetItem Py_PROTO((PyObject *o, PyObject *key, PyObject *v)); /* Map the object, key, to the value, v. Returns -1 on failure. This is the equivalent of the Python statement: o[key]=v. */ int PyObject_DelItem Py_PROTO((PyObject *o, PyObject *key)); /* Delete the mapping for key from *o. Returns -1 on failure. This is the equivalent of the Python statement: del o[key]. */ /* Number Protocol:*/ int PyNumber_Check Py_PROTO((PyObject *o)); /* Returns 1 if the object, o, provides numeric protocols, and false otherwise. This function always succeeds. */ PyObject *PyNumber_Add Py_PROTO((PyObject *o1, PyObject *o2)); /* Returns the result of adding o1 and o2, or null on failure. This is the equivalent of the Python expression: o1+o2. */ PyObject *PyNumber_Subtract Py_PROTO((PyObject *o1, PyObject *o2)); /* Returns the result of subtracting o2 from o1, or null on failure. This is the equivalent of the Python expression: o1-o2. */ PyObject *PyNumber_Multiply Py_PROTO((PyObject *o1, PyObject *o2)); /* Returns the result of multiplying o1 and o2, or null on failure. This is the equivalent of the Python expression: o1*o2. */ PyObject *PyNumber_Divide Py_PROTO((PyObject *o1, PyObject *o2)); /* Returns the result of dividing o1 by o2, or null on failure. This is the equivalent of the Python expression: o1/o2. */ PyObject *PyNumber_Remainder Py_PROTO((PyObject *o1, PyObject *o2)); /* Returns the remainder of dividing o1 by o2, or null on failure. This is the equivalent of the Python expression: o1%o2. */ PyObject *PyNumber_Divmod Py_PROTO((PyObject *o1, PyObject *o2)); /* See the built-in function divmod. Returns NULL on failure. This is the equivalent of the Python expression: divmod(o1,o2). */ PyObject *PyNumber_Power Py_PROTO((PyObject *o1, PyObject *o2, PyObject *o3)); /* See the built-in function pow. Returns NULL on failure. This is the equivalent of the Python expression: pow(o1,o2,o3), where o3 is optional. */ PyObject *PyNumber_Negative Py_PROTO((PyObject *o)); /* Returns the negation of o on success, or null on failure. This is the equivalent of the Python expression: -o. */ PyObject *PyNumber_Positive Py_PROTO((PyObject *o)); /* Returns the (what?) of o on success, or NULL on failure. This is the equivalent of the Python expression: +o. */ PyObject *PyNumber_Absolute Py_PROTO((PyObject *o)); /* Returns the absolute value of o, or null on failure. This is the equivalent of the Python expression: abs(o). */ PyObject *PyNumber_Invert Py_PROTO((PyObject *o)); /* Returns the bitwise negation of o on success, or NULL on failure. This is the equivalent of the Python expression: ~o. */ PyObject *PyNumber_Lshift Py_PROTO((PyObject *o1, PyObject *o2)); /* Returns the result of left shifting o1 by o2 on success, or NULL on failure. This is the equivalent of the Python expression: o1 << o2. */ PyObject *PyNumber_Rshift Py_PROTO((PyObject *o1, PyObject *o2)); /* Returns the result of right shifting o1 by o2 on success, or NULL on failure. This is the equivalent of the Python expression: o1 >> o2. */ PyObject *PyNumber_And Py_PROTO((PyObject *o1, PyObject *o2)); /* Returns the result of "anding" o2 and o2 on success and NULL on failure. This is the equivalent of the Python expression: o1 and o2. */ PyObject *PyNumber_Xor Py_PROTO((PyObject *o1, PyObject *o2)); /* Returns the bitwise exclusive or of o1 by o2 on success, or NULL on failure. This is the equivalent of the Python expression: o1^o2. */ PyObject *PyNumber_Or Py_PROTO((PyObject *o1, PyObject *o2)); /* Returns the result or o1 and o2 on success, or NULL on failure. This is the equivalent of the Python expression: o1 or o2. */ /* Implemented elsewhere: int PyNumber_Coerce(PyObject **p1, PyObject **p2); This function takes the addresses of two variables of type PyObject*. If the objects pointed to by *p1 and *p2 have the same type, increment their reference count and return 0 (success). If the objects can be converted to a common numeric type, replace *p1 and *p2 by their converted value (with 'new' reference counts), and return 0. If no conversion is possible, or if some other error occurs, return -1 (failure) and don't increment the reference counts. The call PyNumber_Coerce(&o1, &o2) is equivalent to the Python statement o1, o2 = coerce(o1, o2). */ PyObject *PyNumber_Int Py_PROTO((PyObject *o)); /* Returns the o converted to an integer object on success, or NULL on failure. This is the equivalent of the Python expression: int(o). */ PyObject *PyNumber_Long Py_PROTO((PyObject *o)); /* Returns the o converted to a long integer object on success, or NULL on failure. This is the equivalent of the Python expression: long(o). */ PyObject *PyNumber_Float Py_PROTO((PyObject *o)); /* Returns the o converted to a float object on success, or NULL on failure. This is the equivalent of the Python expression: float(o). */ /* Sequence protocol:*/ int PySequence_Check Py_PROTO((PyObject *o)); /* Return 1 if the object provides sequence protocol, and zero otherwise. This function always succeeds. */ int PySequence_Length Py_PROTO((PyObject *o)); /* Return the length of sequence object o, or -1 on failure. */ PyObject *PySequence_Concat Py_PROTO((PyObject *o1, PyObject *o2)); /* Return the concatination of o1 and o2 on success, and NULL on failure. This is the equivalent of the Python expression: o1+o2. */ PyObject *PySequence_Repeat Py_PROTO((PyObject *o, int count)); /* Return the result of repeating sequence object o count times, or NULL on failure. This is the equivalent of the Python expression: o1*count. */ PyObject *PySequence_GetItem Py_PROTO((PyObject *o, int i)); /* Return the ith element of o, or NULL on failure. This is the equivalent of the Python expression: o[i]. */ PyObject *PySequence_GetSlice Py_PROTO((PyObject *o, int i1, int i2)); /* Return the slice of sequence object o between i1 and i2, or NULL on failure. This is the equivalent of the Python expression: o[i1:i2]. */ int PySequence_SetItem Py_PROTO((PyObject *o, int i, PyObject *v)); /* Assign object v to the ith element of o. Returns -1 on failure. This is the equivalent of the Python statement: o[i]=v. */ int PySequence_DelItem Py_PROTO((PyObject *o, int i)); /* Delete the ith element of object v. Returns -1 on failure. This is the equivalent of the Python statement: del o[i]. */ int PySequence_SetSlice Py_PROTO((PyObject *o, int i1, int i2, PyObject *v)); /* Assign the sequence object, v, to the slice in sequence object, o, from i1 to i2. Returns -1 on failure. This is the equivalent of the Python statement: o[i1:i2]=v. */ int PySequence_DelSlice Py_PROTO((PyObject *o, int i1, int i2)); /* Delete the slice in sequence object, o, from i1 to i2. Returns -1 on failure. This is the equivalent of the Python statement: del o[i1:i2]. */ PyObject *PySequence_Tuple Py_PROTO((PyObject *o)); /* Returns the o as a tuple on success, and NULL on failure. This is equivalent to the Python expression: tuple(o) */ int PySequence_Count Py_PROTO((PyObject *o, PyObject *value)); /* Return the number of occurrences on value on o, that is, return the number of keys for which o[key]==value. On failure, return -1. This is equivalent to the Python expression: o.count(value). */ int PySequence_In Py_PROTO((PyObject *o, PyObject *value)); /* Determine if o contains value. If an item in o is equal to X, return 1, otherwise return 0. On error, return -1. This is equivalent to the Python expression: value in o. */ int PySequence_Index Py_PROTO((PyObject *o, PyObject *value)); /* Return the first index for which o[i]=value. On error, return -1. This is equivalent to the Python expression: o.index(value). */ /* Mapping protocol:*/ int PyMapping_Check Py_PROTO((PyObject *o)); /* Return 1 if the object provides mapping protocol, and zero otherwise. This function always succeeds. */ int PyMapping_Length Py_PROTO((PyObject *o)); /* Returns the number of keys in object o on success, and -1 on failure. For objects that do not provide sequence protocol, this is equivalent to the Python expression: len(o). */ int PyMapping_DelItemString Py_PROTO((PyObject *o, char *key)); /* Remove the mapping for object, key, from the object *o. Returns -1 on failure. This is equivalent to the Python statement: del o[key]. */ int PyMapping_DelItem Py_PROTO((PyObject *o, PyObject *key)); /* Remove the mapping for object, key, from the object *o. Returns -1 on failure. This is equivalent to the Python statement: del o[key]. */ int PyMapping_HasKeyString Py_PROTO((PyObject *o, char *key)); /* On success, return 1 if the mapping object has the key, key, and 0 otherwise. This is equivalent to the Python expression: o.has_key(key). This function always succeeds. */ int PyMapping_HasKey Py_PROTO((PyObject *o, PyObject *key)); /* Return 1 if the mapping object has the key, key, and 0 otherwise. This is equivalent to the Python expression: o.has_key(key). This function always succeeds. */ /* Implemented as macro: PyObject *PyMapping_Keys(PyObject *o); On success, return a list of the keys in object o. On failure, return NULL. This is equivalent to the Python expression: o.keys(). */ #define PyMapping_Keys(O) PyObject_CallMethod(O,"keys",NULL) /* Implemented as macro: PyObject *PyMapping_Values(PyObject *o); On success, return a list of the values in object o. On failure, return NULL. This is equivalent to the Python expression: o.values(). */ #define PyMapping_Values(O) PyObject_CallMethod(O,"values",NULL) /* Implemented as macro: PyObject *PyMapping_Items(PyObject *o); On success, return a list of the items in object o, where each item is a tuple containing a key-value pair. On failure, return NULL. This is equivalent to the Python expression: o.items(). */ #define PyMapping_Items(O) PyObject_CallMethod(O,"items",NULL) PyObject *PyMapping_GetItemString Py_PROTO((PyObject *o, char *key)); /* Return element of o corresponding to the object, key, or NULL on failure. This is the equivalent of the Python expression: o[key]. */ int PyMapping_SetItemString Py_PROTO((PyObject *o, char *key, PyObject *value)); /* Map the object, key, to the value, v. Returns -1 on failure. This is the equivalent of the Python statement: o[key]=v. */ #ifdef __cplusplus } #endif #endif /* Py_ABSTRACTOBJECT_H */