pandas LabelEncoder方法，对离散值进行编码，并储存

# 3.离散值进行LabelEncoder  #处理数据的三个步骤，去重，处理缺失值，离散值LabelEncoder

from sklearn import preprocessing
from sklearn.externals import joblib

categorical_ix = ["1","2","3"]  #离散值的列名

for i in categorical_ix:
    le = preprocessing.LabelEncoder()
    k = le.fit_transform(df_train[i])
    joblib.dump(le,i+"_LabelEncoder.model")
    df_train[i] = k

for i in categorical_ix:
    le = joblib.load(i+"_LabelEncoder.model")
    k = le.transform(df_train[i])
    df_test[i] = k