pandas LabelEncoder方法，對離散值進行編碼，並儲存

# 3.離散值進行LabelEncoder  #處理數據的三個步驟，去重，處理缺失值，離散值LabelEncoder

from sklearn import preprocessing
from sklearn.externals import joblib

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

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