object_meta.md

# Python 获取对象信息

过滤列表里所有含有 'z' 属性的对象，打印他们的 'x'+'y'+'z' 的值

```python
# -*- coding: UTF-8 -*-
class Point2D:
    def __init__(self, x, y) -> None:
        self.x = x
        self.y = y

class Point3D:
    def __init__(self, x, y, z) -> None:
        self.x = x
        self.y = y
        self.z = z

class Vector2D:
    def __init__(self, x, y) -> None:
        self.x = x
        self.y = y

class Vector3D:
    def __init__(self, x, y, z) -> None:
        self.x = x
        self.y = y
        self.z = z

def test():
    points = [
        Point2D(0, 1),
        Point2D(0, 1),
        Point3D(0, 1, 2),
        Point3D(0, 1, 3),
        Vector2D(0, 1),
        Vector3D(0, 1, 4),
    ]

    z_objects = []
    # TODO(You): 请在此过滤出含有'z'属性的对象，在过滤中打印出对应对象的'z'属性

    for p in z_objects:
        print('x+y+z:', p.x+p.y+p.z)

if __name__ == '__main__':
    test()
```

请选出下列能**正确**实现这一功能的选项。

## template

```python

class Point2D:
    def __init__(self, x, y) -> None:
        self.x = x
        self.y = y


class Point3D:
    def __init__(self, x, y, z) -> None:
        self.x = x
        self.y = y
        self.z = z


class Vector2D:
    def __init__(self, x, y) -> None:
        self.x = x
        self.y = y


class Vector3D:
    def __init__(self, x, y, z) -> None:
        self.x = x
        self.y = y
        self.z = z


def test():
    points = [
        Point2D(0, 1),
        Point2D(0, 1),
        Point3D(0, 1, 2),
        Point3D(0, 1, 3),
        Vector2D(0, 1),
        Vector3D(0, 1, 4),
    ]

    z_objects = []
    for p in points:
        if hasattr(p, 'z'):
            z = getattr(p, 'z')
            print('get z attr:', z)
            z_objects.append(p)

    for p in z_objects:
        print('x+y+z:', p.x+p.y+p.z)

if __name__ == '__main__':
    test()
```

## 答案

```python
for p in points:
    if hasattr(p, 'z'):
        z = getattr(p, 'z')
        print('get z attr:', z)
        z_objects.append(p)
```

## 选项

### A

```python
for p in points:
    z = getattr(p, 'z')
    print('get z attr:', z)
    z_objects.append(p)
```

### B

```python
for p in points:
    if not hasattr(p, 'z'):
        z = getattr(p, 'z')
        print('get z attr:', z)
        z_objects.append(p)
```

### C

```python
for p in points:
    if p.hasattr('z'):
        z = p.getattr(p, 'z')
        print('get z attr:', z)
        z_objects.append(p)
```