python - Pandas MultiIndex 获取所有一个 0 级列和一个特定列

Question

我有一个 pandas DataFrame，列上有一个 MultiIndex，我想访问 bar 的所有列以及 baz 下的一个附加列> - 我怎样才能做到这一点？

输入:

import numpy as np
import pandas as pd

np.random.seed(123)
iterables = [["bar", "baz", "foo", "qux"], ["one", "two"]]
idx = pd.MultiIndex.from_product(iterables, names=["first", "second"])
df = pd.DataFrame(np.random.randn(4, 8), columns=idx)

first        bar                 baz                 foo                 qux
second       one       two       one       two       one       two       one       two
0      -1.085631  0.997345  0.282978 -1.506295 -0.578600  1.651437 -2.426679 -0.428913
1       1.265936 -0.866740 -0.678886 -0.094709  1.491390 -0.638902 -0.443982 -0.434351
2       2.205930  2.186786  1.004054  0.386186  0.737369  1.490732 -0.935834  1.175829
3      -1.253881 -0.637752  0.907105 -1.428681 -0.140069 -0.861755 -0.255619 -2.798589

预期输出:

first        bar                 baz
second       one       two       two
0      -1.085631  0.997345 -1.506295
1       1.265936 -0.866740 -0.094709
2       2.205930  2.186786  0.386186
3      -1.253881 -0.637752 -1.428681

我可以指定特定的列，例如 df.loc[:, [("bar", "one"), ("bar", "two"), ("baz", "two")]] 但我似乎不能只为一个顶级指定任意数字，例如 df.loc[:, ["bar", ("baz", "two")]]

Answer 1

iloc解决方案

ix = df.columns.get_loc
df.iloc[:, np.r_[ix('bar'), ix(('baz', 'two'))]]

---

first        bar                 baz
second       one       two       two
0      -1.085631  0.997345 -1.506295
1       1.265936 -0.866740 -0.094709
2       2.205930  2.186786  0.386186
3      -1.253881 -0.637752 -1.428681