Question

可能不相关的java.awt.event.ActionEvent内部。

#include <Python.h>
#include <structmember.h>

#define ARRLEN(x) sizeof(x)/sizeof(x[0])


typedef struct {
    PyObject_HEAD
    PyTypeObject base;
} MetaObject;

typedef struct {
    PyObject_HEAD
} ParentObject;


static PyObject *Meta_call(MetaObject *type, PyObject *args, PyObject *kwargs) {
    PyObject *obj = PyType_GenericNew((PyTypeObject *) type, args, kwargs);

    // Only do checks for subclasses of Parent
    if (strcmp(obj->ob_type->tp_name, "Parent") == 0)
        return obj;

    // Get obj's attributes
    PyObject *obj_dir = PyObject_Dir(obj);
    if (obj_dir == NULL)
        return NULL;

    char *required_attrs[] = {"x"};

    // Raise an exception of obj doesn't define all required_attrs
    PyObject *attr_obj;
    int has_attr;
    for (int i=0; i<ARRLEN(required_attrs); i++) {
        attr_obj = PyUnicode_FromString(required_attrs[i]);
        has_attr = PySequence_Contains(obj_dir, attr_obj);
        if (has_attr == 0) {
            printf("Subclasses of Parent must define %s\n", required_attrs[i]);
            // raise NotImplementedError
            return NULL;
        } else if (has_attr == -1) {
            return NULL;
        }
    }

    return obj;
}


static PyTypeObject MetaType = {
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "custom.Meta",
    .tp_basicsize = sizeof(MetaObject),
    .tp_itemsize = 0,
    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
    .tp_new = PyType_GenericNew,
    .tp_call = (ternaryfunc) Meta_call,
};

static PyTypeObject ParentType = {
    PyVarObject_HEAD_INIT(&MetaType, 0)
    .tp_name = "custom.Parent",
    .tp_basicsize = sizeof(ParentObject),
    .tp_itemsize = 0,
    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
    .tp_new = PyType_GenericNew,
};


static PyModuleDef custommodule = {
    PyModuleDef_HEAD_INIT,
    .m_name = "custom",
    .m_size = -1,
};


PyMODINIT_FUNC PyInit_custom(void) {
    PyObject *module = PyModule_Create(&custommodule);
    if (module == NULL)
        return NULL;

    MetaType.tp_base = &PyType_Type;
    if (PyType_Ready(&MetaType) < 0)
        return NULL;
    Py_INCREF(&MetaType);
    PyModule_AddObject(module, "Meta", (PyObject *) &MetaType);

    if (PyType_Ready(&ParentType) < 0)
        return NULL;
    Py_INCREF(&ParentType);
    PyModule_AddObject(module, "Parent", (PyObject *) &ParentType);

    return module;
}

输出为：空存储 filename.txt filtname2.txt

如果我们更改String路径=“”;

输出到。藏 filename.txt filename2.txt

为什么第一个输出添加“ null”？

Answer 1

String的默认值为null，在打印时它的字面意思是null。从测试结果中可以看到，将其更改为""（空字符串）后，即会打印出来。

当您附加到null的字符串时，它将像stash一样将文本null粘贴在null.stash之后。

文件对象getname的数组列表为null字符串问题

1 个答案: