pandas - 在所有列中获取虚拟值

Question

get dummies 方法在使用多于一列时似乎无法按预期工作。
例如如果我有这个数据框...

shopping_list = [
    ["Apple", "Bread", "Fridge"],
    ["Rice", "Bread", "Milk"],
    ["Apple", "Rice", "Bread", "Milk"],
    ["Rice", "Milk"],
    ["Apple", "Bread", "Milk"],
]

df = pd.DataFrame(shopping_list)

如果我使用 get_dummmies 方法，这些项目会在列中重复，如下所示:

pd.get_dummies(df)

    0_Apple 0_Rice  1_Bread 1_Milk  1_Rice  2_Bread 2_Fridge    2_Milk  3_Milk
0   1   0   1   0   0   0   1   0   0
1   0   1   1   0   0   0   0   1   0
2   1   0   0   0   1   1   0   0   1
3   0   1   0   1   0   0   0   0   0
4   1   0   1   0   0   0   0   1   0

虽然预期的结果是:

    Apple Bread Fridge Milk Rice
0 1 1 1 0 0 
1 0 1 0 1 1
2 1 1 0 1 1
3 0 0 0 1 1
4 1 1 0 1 0

Answer 1

添加参数 prefix和 prefix_sep至 get_dummies 然后添加 max为了避免重复的列名(它由 max 聚合):

df = pd.get_dummies(df, prefix='', prefix_sep='').max(axis=1, level=0)
print(df)

   Apple  Rice  Bread  Milk  Fridge
0      1     0      1     0       1
1      0     1      1     1       0
2      1     1      1     1       0
3      0     1      0     1       0
4      1     0      1     1       0