熊猫，python:如何对包含字符串数组的列进行一次热编码

Question

我想知道如何对包含字符串数组的列进行一次热编码。

我正在尝试从df到df2：

import pandas as pd

# This is the original data frame
df = pd.DataFrame({'menu': [['Italian', 'Greek'], ['Japanese'],
                   ['Italian','Greek', 'Japanese']], 'price': ['$$', '$$', '$']})

df.head()

# This is the desired result

df2 = pd.DataFrame({'menu': [['Italian', 'Greek'], ['Japanese'], 
['Italian','Greek', 'Japanese']], 
                    'price': ['$$', '$$', '$'], 
                    'Italian': [1,0,1],
                    'Greek': [1,0,1],
                    'Japanese': [0,1,1]
                   })
df2.head()

Answer 1

将MultiLabelBinarizer与join结合使用

from sklearn.preprocessing import MultiLabelBinarizer

mlb = MultiLabelBinarizer()
df = df.join(pd.DataFrame(mlb.fit_transform(df['menu']),columns=mlb.classes_))
print (df)
                         menu price  Greek  Italian  Japanese
0            [Italian, Greek]    $$      1        1         0
1                  [Japanese]    $$      0        0         1
2  [Italian, Greek, Japanese]     $      1        1         1

Answer 2

您可以使用pd.get_dummies、pd.apply、DataFrame.join和Series.stack

df.join(pd.get_dummies(df.menu.apply(pd.Series).stack()).sum(level=0))

输出：

                         menu price  Greek  Italian  Japanese
0            [Italian, Greek]    $$      1        1         0
1                  [Japanese]    $$      0        0         1
2  [Italian, Greek, Japanese]     $      1        1         1