从dataframe创建多索引

import pandas as pd

data = {
    ('A', 'a'): [1, 2, 3],
    ('A', 'b'): [4, 5, 6],
    ('B', 'a'): [7, 8, 9],
    ('B', 'b'): [10, 11, 12]
}

df = pd.DataFrame.from_dict(data)

import pandas as pd

data = [
    ('A', 'a', 1),
    ('A', 'b', 4),
    ('B', 'a', 7),
    ('B', 'b', 10)
]

df = pd.DataFrame.from_records(data, columns=['Level 1', 'Level 2', 'Value'])

import pandas as pd

data = {
    'Level 1': ['A', 'A', 'B', 'B'],
    'Level 2': ['a', 'b', 'a', 'b'],
    'Value': [1, 4, 7, 10]
}

df = pd.DataFrame(data)
df = df.set_index(['Level 1', 'Level 2'])