在元组的numpy数组中的给定位置查找唯一值

Question

我有一个numpy数组，看起来像这样：

[
('{893EE51E-0CD1-4C06-B672-365EECA26C33}', 'image/jpeg', 'Photo1.jpg', []),
('{893EE51E-0CD1-4C06-B672-365EECA26C33}', 'image/jpeg', 'Photo2.jpg', []),
('{893EE51E-0CD1-4C06-B672-365EECA26C63}', 'image/jpeg', 'Photo1.jpg', []),
('{893EE51E-0CD1-4C06-B672-365EECA26C73}', 'image/jpeg', 'Photo1.jpg', [])
]

如何在每个元组的“位置0”处找到唯一值？理想情况下，我希望输出如下所示的数组（或列表）：

[
'{893EE51E-0CD1-4C06-B672-365EECA26C33}',
'{893EE51E-0CD1-4C06-B672-365EECA26C63}',
'{893EE51E-0CD1-4C06-B672-365EECA26C73}'
]

Answer 1

从显示器重新创建结构化阵列：

In [241]: _ = np.array([
     ...: ('{893EE51E-0CD1-4C06-B672-365EECA26C33}', 'image/jpeg', 'Photo1.jpg', []),
     ...: ('{893EE51E-0CD1-4C06-B672-365EECA26C33}', 'image/jpeg', 'Photo2.jpg', []),
     ...: ('{893EE51E-0CD1-4C06-B672-365EECA26C63}', 'image/jpeg', 'Photo1.jpg', []),
     ...: ('{893EE51E-0CD1-4C06-B672-365EECA26C73}', 'image/jpeg', 'Photo1.jpg', [])
     ...: ],dtype='U50,U20,U20,O')
Out[241]: 
array([('{893EE51E-0CD1-4C06-B672-365EECA26C33}', 'image/jpeg', 'Photo1.jpg', list([])),
       ('{893EE51E-0CD1-4C06-B672-365EECA26C33}', 'image/jpeg', 'Photo2.jpg', list([])),
       ('{893EE51E-0CD1-4C06-B672-365EECA26C63}', 'image/jpeg', 'Photo1.jpg', list([])),
       ('{893EE51E-0CD1-4C06-B672-365EECA26C73}', 'image/jpeg', 'Photo1.jpg', list([]))],
      dtype=[('f0', '<U50'), ('f1', '<U20'), ('f2', '<U20'), ('f3', 'O')])

选择第一个字段：

In [242]: _['f0']
Out[242]: 
array(['{893EE51E-0CD1-4C06-B672-365EECA26C33}',
       '{893EE51E-0CD1-4C06-B672-365EECA26C33}',
       '{893EE51E-0CD1-4C06-B672-365EECA26C63}',
       '{893EE51E-0CD1-4C06-B672-365EECA26C73}'], dtype='<U50')

将unique应用于：

In [243]: np.unique(_)
Out[243]: 
array(['{893EE51E-0CD1-4C06-B672-365EECA26C33}',
       '{893EE51E-0CD1-4C06-B672-365EECA26C63}',
       '{893EE51E-0CD1-4C06-B672-365EECA26C73}'], dtype='<U50')

Answer 2

在切片第一列后使用^{}（[:, 0]）

>>> np.unique(arr[:,0])

array(['{893EE51E-0CD1-4C06-B672-365EECA26C33}',
       '{893EE51E-0CD1-4C06-B672-365EECA26C63}',
       '{893EE51E-0CD1-4C06-B672-365EECA26C73}'], dtype=object)

Answer 3

将set（）与列表理解结合使用：

x = [
('{893EE51E-0CD1-4C06-B672-365EECA26C33}', 'image/jpeg', 'Photo1.jpg', []),
('{893EE51E-0CD1-4C06-B672-365EECA26C33}', 'image/jpeg', 'Photo2.jpg', []),
('{893EE51E-0CD1-4C06-B672-365EECA26C63}', 'image/jpeg', 'Photo1.jpg', []),
('{893EE51E-0CD1-4C06-B672-365EECA26C73}', 'image/jpeg', 'Photo1.jpg', [])
]
y = set(i[0] for i in x)
y
{'{893EE51E-0CD1-4C06-B672-365EECA26C63}',
 '{893EE51E-0CD1-4C06-B672-365EECA26C73}',
 '{893EE51E-0CD1-4C06-B672-365EECA26C33}'}