Python Pandas – 返回多重索引中所要求层级的标签值向量

要返回多重索引中所要求层级的标签值向量，请使用multiIndex.get_level_values()方法。将层级名称设置为参数即可。

首先，导入所需的库：

import pandas as pd

MultiIndex是用于Pandas对象的多级或分层索引对象。

multiIndex = pd.MultiIndex.from_arrays([list('pqrrss'), list('strvwx')],names=['One', 'Two'])

显示MultiIndex：

print("The MultiIndex...\n",multiIndex)

获取MultiIndex中的级别：

print("\nThe levels in MultiIndex...\n",multiIndex.levels)

获取级别0的等级值：

print("\nLevel values...\n",multiIndex.get_level_values(0))

示例

以下是代码：

import pandas as pd

# MultiIndex is a multi-level, or hierarchical, index object for pandas objects
multiIndex = pd.MultiIndex.from_arrays([list('pqrrss'), list('strvwx')],names=['One', 'Two'])

# display the MultiIndex
print("The MultiIndex...\n",multiIndex)

# get the levels in MultiIndex
print("\nThe levels in MultiIndex...\n",multiIndex.levels)

# get level values at level 0
print("\nLevel values...\n",multiIndex.get_level_values(0))

# get level values with level name "Two"
print("\nLevel values...\n",multiIndex.get_level_values("Two"))

输出

这将产生以下输出：

The MultiIndex...
MultiIndex([('p', 's'),
            ('q', 't'),
            ('r', 'r'),
            ('r', 'v'),
            ('s', 'w'),
            ('s', 'x')],
            names=['One', 'Two'])

The levels in MultiIndex...
   [['p', 'q', 'r', 's'], ['r', 's', 't', 'v', 'w', 'x']]

Level values...
   Index(['p', 'q', 'r', 'r', 's', 's'], dtype='object', name='One')

Level values...
   Index(['s', 't', 'r', 'v', 'w', 'x'], dtype='object', name='Two')