4_1和4_2作为训练集
import pandas as pd
train1 = pd.read_table('question_4_1.txt', sep='\t', header=None)
train2 = pd.read_table('question_4_2.txt', sep='\t', header=None)
train = pd.concat([train1, train2], axis=0)
names = ['text','sentiment']
train.columns = names
