python - Pandas:为列的每个实例创建具有二进制值的数据框

Question

我目前有一个看起来像这样的 DataFrame

user    | preference
----------------
Alex    | tea
Alex    | cookie
Alex    | apple
Peter   | coffee
Peter   | apple
Peter   | banana
John    | tea

我需要将上面的转换为一个 DF，它将用户映射到首选项列的所有唯一值。如果用户有那个偏好，如果不是 0，我们将分配 1。所以，结果应该是这样的

user     | preference | value 
-------------------------
Alex     | tea        | 1
Alex     | coffee     | 0
Alex     | cookie     | 1
Alex     | apple      | 1
Alex     | banana     | 0
Peter    | tea        | 0
Peter    | coffee     | 1
Peter    | cookie     | 0
Peter    | apple      | 1
Peter    | banana     | 1
John     | tea        | 1
John     | coffee     | 0
John     | cookie     | 0
John     | apple      | 0
John     | banana     | 0

Answer 1

尝试:

x = (
    pd.crosstab(df["user"], df["preference"])
    .stack()
    .reset_index()
    .rename(columns={0: "value"})
)
print(x)

打印:

    user preference  value
0      1      apple      1
1      1     banana      0
2      1     coffee      0
3      1     cookie      1
4      1        tea      1
5      2      apple      1
6      2     banana      1
7      2     coffee      1
8      2     cookie      0
9      2        tea      0
10     3      apple      0
11     3     banana      0
12     3     coffee      0
13     3     cookie      0
14     3        tea      1