您可以按照此答案中的说明使用类别：
categories = np.union1d(train, test)
train = train.astype('category', categories=categories)
test = test.astype('category', categories=categories)
pd.get_dummies(train)
Out:
a b c d
0 1 0 0 0
1 0 1 0 0
2 0 1 0 0
3 1 0 0 0
4 1 0 0 0
pd.get_dummies(test)
Out:
a b c d
0 1 0 0 0
1 0 1 0 0
2 0 0 1 0
3 0 0 0 1
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