Python Pandas 合并两个数据帧而不改变顺序

Question

我有两个 pandas Dataframe，一个是 df1，形状 = (35,9)，另一个是 df2，形状 = (12,9)，我想要合并它们。

df2的行索引是:

RangeIndex(start=1, stop=13, step=1)

df1 的行索引为:

Int64Index([    2, 10021, 10022, 10023, 10024,     3, 10021, 10022, 10023,
        10024,     4, 10021, 10022, 10023, 10024,     5, 10021, 10022,
        10023, 10024,     6, 10021, 10022, 10023, 10024,     7, 10021,
        10022, 10023, 10024,     8, 10021, 10022, 10023, 10024],
       dtype='int64')

我想合并这两个数据帧，以便生成的数据帧具有以下索引:

Int64Index([1,2,10021,10022,10023,10024, 3, 10021, 10022, 10023,
        10024,     4, 10021, 10022, 10023, 10024,     5, 10021, 10022,
        10023, 10024,     6, 10021, 10022, 10023, 10024,     7, 10021,
        10022, 10023, 10024,     8, 10021, 10022, 10023, 10024, 9, 10, 11, 12],
       dtype='int64')

Answer 1

我认为您正在寻找外部联接:

import pandas as pd
idx1 = [    2, 10021, 10022, 10023, 10024,     3, 10021, 10022, 10023,
        10024,     4, 10021, 10022, 10023, 10024,     5, 10021, 10022,
        10023, 10024,     6, 10021, 10022, 10023, 10024,     7, 10021,
        10022, 10023, 10024,     8, 10021, 10022, 10023, 10024]
df1 = pd.DataFrame(data={'a': range(len(idx1))},
                   index=idx1)


df2 = pd.DataFrame(data={'b': range(1,13)},
                   index=range(1,13))

result_df = pd.merge(df1, df2, how='outer', left_index=True, right_index=True)
result_df.index
Int64Index([    1,     2,     3,     4,     5,     6,     7,     8,     9,
               10,    11,    12,    13, 10021, 10021, 10021, 10021, 10021,
            10021, 10021, 10022, 10022, 10022, 10022, 10022, 10022, 10022,
            10023, 10023, 10023, 10023, 10023, 10023, 10023, 10024, 10024,
            10024, 10024, 10024, 10024, 10024],
          dtype='int64')