Question

我正在列表中执行for循环，并希望找到匹配并打印下一行。但是，当我尝试使用next（）方法时，我一直都会失败。我可以在指定的匹配后获取下一行的帮助吗？

string（用于循环输出）：

item_0
0
item_1
0           




item_3
727

item_4
325

For Loop查找匹配和下一行：

result = tree.xpath('//tr/td/font/text()')

for line in result:
    if 'item_3' in line:
        print(line.next())

错误：

AttributeError: '_ElementStringResult' object has no attribute 'next'

Answer 1

line是代码中的lxml.etree._ElementStringResult（修改后的str）。 lxml.etree._ElementStringResults没有next方法，这就是您获得AttributeError的原因。

您可以设置一个标志，指示下一行应按如下方式打印：

print_line = False
for line in result:
    if print_line:
        print(line)
        print_line = False
    if 'item_3' in line:
        print_line = True

Answer 2

没有测试过，但请尝试：

//virtual base class
class Base {
public :
    virtual void f() {
        cout << "Base::f()" << endl;
    }
private:
    long x;
};

//derived class
class Derived : public virtual Base {
public:
    virtual void f() {
        cout << "Derived::f()" << endl;
    }
private:
    long y;
};

int main() {
    typedef void (*FUNC)(void);
    Derived d;

    //In my machine, sizeof(long) == sizeof(pointers). My code below is neither portable nor concise. You can just read the annotation.

    //dereference the first element of the first virtual function table(equals to *(vptr1->slot[0]))
    cout << hex << *((long*)*((long*)(&d) + 0) + 0) << endl;
    ((FUNC)*((long*)*((long*)(&d) + 0) + 0))();//invoke Derived::f()

    //dereference the first element of the second virtual function table(equals to *(vptr2->slot[0]))
    cout << hex << *((long*)*((long*)(&d) + 2) + 0) << endl;
    ((FUNC)*((long*)*((long*)(&d) + 2) + 0))();//maybe Derived::f()?

    return 0;
}

从for循环打印时，Python打印下一行

2 个答案: