Python pandas 通过多个动态列旋转 DataFrame

发布于05月10日

我想以一种更充分的方式实现下面这样的目标.我想是的.pivot也许能做到，但我做不到.有什么建议吗？

import pandas as pd
df = pd.DataFrame({'level1':['a', 'a'], 'level2':['b', 'b'], 'level3':[100, 101], 'id1':[111,222],'id2':[333,444], 'foo_value':[0.1,0.2], 'bar_value':[0.3,0.4]})

# now i want to re-shape it to below
rows = []
items = [col.replace("_value", "") for col in df.columns if col.endswith("_value")]
for _, row in df.iterrows():
    for id_col in ("id1", "id2"):
        for item in items:
            rows.append({
                "id": row[id_col],
                "item": item,
                "value": row[f"{item}_value"],
                "level1": row["level1"],
                "level2": row["level2"],
                "level3": row["level3"]
            })
reshaped_df = pd.DataFrame(rows)

`数据帧.熔化`

l = ['level1', 'level2', 'level3']
s1 = df.melt(l, value_vars=df.filter(like='id'), value_name='id')
s2 = df.melt(l, value_vars=df.filter(like='_value'), var_name='item')

out = s1.merge(s2).drop('variable', axis=1)

后果

print(out)

  level1 level2  level3   id       item  value
0      a      b     100  111  foo_value    0.1
1      a      b     100  111  bar_value    0.3
2      a      b     100  333  foo_value    0.1
3      a      b     100  333  bar_value    0.3
4      a      b     101  222  foo_value    0.2
5      a      b     101  222  bar_value    0.4
6      a      b     101  444  foo_value    0.2
7      a      b     101  444  bar_value    0.4