#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 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) DL_IMPORT(int) PyObject_Cmp(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. */ DL_IMPORT(int) PyCallable_Check(PyObject *o); /* Determine if the object, o, is callable. Return 1 if the object is callable and 0 otherwise. This function always succeeds. */ DL_IMPORT(PyObject *) PyObject_CallObject(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). */ DL_IMPORT(PyObject *) PyObject_CallFunction(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). */ DL_IMPORT(PyObject *) PyObject_CallMethod(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. */ /* Implemented elsewhere: int PyObject_Not(PyObject *o); Returns 0 if the object, o, is considered to be true, and 1 otherwise. This is equivalent to the Python expression: not o This function always succeeds. */ DL_IMPORT(PyObject *) PyObject_Type(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). */ DL_IMPORT(int) PyObject_Size(PyObject *o); /* Return the size of object o. If the object, o, provides both sequence and mapping protocols, the sequence size is returned. On error, -1 is returned. This is the equivalent to the Python expression: len(o). */ /* For DLL compatibility */ #undef PyObject_Length DL_IMPORT(int) PyObject_Length(PyObject *o); #define PyObject_Length PyObject_Size DL_IMPORT(PyObject *) PyObject_GetItem(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]. */ DL_IMPORT(int) PyObject_SetItem(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. */ DL_IMPORT(int) PyObject_DelItem(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]. */ DL_IMPORT(int) PyObject_AsCharBuffer(PyObject *obj, const char **buffer, int *buffer_len); /* Takes an arbitrary object which must support the (character, single segment) buffer interface and returns a pointer to a read-only memory location useable as character based input for subsequent processing. 0 is returned on success. buffer and buffer_len are only set in case no error occurrs. Otherwise, -1 is returned and an exception set. */ DL_IMPORT(int) PyObject_AsReadBuffer(PyObject *obj, const void **buffer, int *buffer_len); /* Same as PyObject_AsCharBuffer() except that this API expects (readable, single segment) buffer interface and returns a pointer to a read-only memory location which can contain arbitrary data. 0 is returned on success. buffer and buffer_len are only set in case no error occurrs. Otherwise, -1 is returned and an exception set. */ DL_IMPORT(int) PyObject_AsWriteBuffer(PyObject *obj, void **buffer, int *buffer_len); /* Takes an arbitrary object which must support the (writeable, single segment) buffer interface and returns a pointer to a writeable memory location in buffer of size buffer_len. 0 is returned on success. buffer and buffer_len are only set in case no error occurrs. Otherwise, -1 is returned and an exception set. */ /* Number Protocol:*/ DL_IMPORT(int) PyNumber_Check(PyObject *o); /* Returns 1 if the object, o, provides numeric protocols, and false otherwise. This function always succeeds. */ DL_IMPORT(PyObject *) PyNumber_Add(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. */ DL_IMPORT(PyObject *) PyNumber_Subtract(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. */ DL_IMPORT(PyObject *) PyNumber_Multiply(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. */ DL_IMPORT(PyObject *) PyNumber_Divide(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. */ DL_IMPORT(PyObject *) PyNumber_Remainder(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. */ DL_IMPORT(PyObject *) PyNumber_Divmod(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). */ DL_IMPORT(PyObject *) PyNumber_Power(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. */ DL_IMPORT(PyObject *) PyNumber_Negative(PyObject *o); /* Returns the negation of o on success, or null on failure. This is the equivalent of the Python expression: -o. */ DL_IMPORT(PyObject *) PyNumber_Positive(PyObject *o); /* Returns the (what?) of o on success, or NULL on failure. This is the equivalent of the Python expression: +o. */ DL_IMPORT(PyObject *) PyNumber_Absolute(PyObject *o); /* Returns the absolute value of o, or null on failure. This is the equivalent of the Python expression: abs(o). */ DL_IMPORT(PyObject *) PyNumber_Invert(PyObject *o); /* Returns the bitwise negation of o on success, or NULL on failure. This is the equivalent of the Python expression: ~o. */ DL_IMPORT(PyObject *) PyNumber_Lshift(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. */ DL_IMPORT(PyObject *) PyNumber_Rshift(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. */ DL_IMPORT(PyObject *) PyNumber_And(PyObject *o1, PyObject *o2); /* Returns the result of bitwise and of o1 and o2 on success, or NULL on failure. This is the equivalent of the Python expression: o1&o2. */ DL_IMPORT(PyObject *) PyNumber_Xor(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. */ DL_IMPORT(PyObject *) PyNumber_Or(PyObject *o1, PyObject *o2); /* Returns the result of bitwise or or o1 and o2 on success, or NULL on failure. This is the equivalent of the Python expression: o1|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). */ DL_IMPORT(PyObject *) PyNumber_Int(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). */ DL_IMPORT(PyObject *) PyNumber_Long(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). */ DL_IMPORT(PyObject *) PyNumber_Float(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:*/ DL_IMPORT(int) PySequence_Check(PyObject *o); /* Return 1 if the object provides sequence protocol, and zero otherwise. This function always succeeds. */ DL_IMPORT(int) PySequence_Size(PyObject *o); /* Return the size of sequence object o, or -1 on failure. */ /* For DLL compatibility */ #undef PySequence_Length DL_IMPORT(int) PySequence_Length(PyObject *o); #define PySequence_Length PySequence_Size DL_IMPORT(PyObject *) PySequence_Concat(PyObject *o1, PyObject *o2); /* Return the concatenation of o1 and o2 on success, and NULL on failure. This is the equivalent of the Python expression: o1+o2. */ DL_IMPORT(PyObject *) PySequence_Repeat(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. */ DL_IMPORT(PyObject *) PySequence_GetItem(PyObject *o, int i); /* Return the ith element of o, or NULL on failure. This is the equivalent of the Python expression: o[i]. */ DL_IMPORT(PyObject *) PySequence_GetSlice(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]. */ DL_IMPORT(int) PySequence_SetItem(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. */ DL_IMPORT(int) PySequence_DelItem(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]. */ DL_IMPORT(int) PySequence_SetSlice(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. */ DL_IMPORT(int) PySequence_DelSlice(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]. */ DL_IMPORT(PyObject *) PySequence_Tuple(PyObject *o); /* Returns the sequence, o, as a tuple on success, and NULL on failure. This is equivalent to the Python expression: tuple(o) */ DL_IMPORT(PyObject *) PySequence_List(PyObject *o); /* Returns the sequence, o, as a list on success, and NULL on failure. This is equivalent to the Python expression: list(o) */ DL_IMPORT(PyObject *) PySequence_Fast(PyObject *o, const char* m); /* Returns the sequence, o, as a tuple, unless it's already a tuple or list. Use PySequence_Fast_GET_ITEM to access the members of this list. Returns NULL on failure. If the object is not a sequence, raises a TypeError exception with m as the message text. */ #define PySequence_Fast_GET_ITEM(o, i)\ (PyList_Check(o) ? PyList_GET_ITEM(o, i) : PyTuple_GET_ITEM(o, i)) /* Return the ith element of o, assuming that o was returned by PySequence_Fast, and that i is within bounds. */ DL_IMPORT(int) PySequence_Count(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). */ DL_IMPORT(int) PySequence_Contains(PyObject *o, PyObject *value); /* For DLL-level backwards compatibility */ #undef PySequence_In DL_IMPORT(int) PySequence_In(PyObject *o, PyObject *value); /* For source-level backwards compatibility */ #define PySequence_In PySequence_Contains /* 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. */ DL_IMPORT(int) PySequence_Index(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:*/ DL_IMPORT(int) PyMapping_Check(PyObject *o); /* Return 1 if the object provides mapping protocol, and zero otherwise. This function always succeeds. */ DL_IMPORT(int) PyMapping_Size(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). */ /* For DLL compatibility */ #undef PyMapping_Length DL_IMPORT(int) PyMapping_Length(PyObject *o); #define PyMapping_Length PyMapping_Size /* implemented as a macro: int PyMapping_DelItemString(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]. */ #define PyMapping_DelItemString(O,K) PyDict_DelItemString((O),(K)) /* implemented as a macro: int PyMapping_DelItem(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]. */ #define PyMapping_DelItem(O,K) PyDict_DelItem((O),(K)) DL_IMPORT(int) PyMapping_HasKeyString(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. */ DL_IMPORT(int) PyMapping_HasKey(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) DL_IMPORT(PyObject *) PyMapping_GetItemString(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]. */ DL_IMPORT(int) PyMapping_SetItemString(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 */