嗨，任何看到我的问题的人，请提前。
我在“ financial_tag ”列中分别有3个csv文件don't have Missing values，但在contat之后。**
代码在这里：
import pandas as pd
dt1 = pd.read_csv('f:\Sep.csv', encoding='gbk', low_memory=False)
dt2 = pd.read_csv('f:\Aug.csv', encoding='gbk', low_memory=False)
dt3 = pd.read_csv('f:\Jul.csv', encoding='gbk', low_memory=False)
a = dt1.loc[(dt1['financial_tag'] != 157)
& (dt1['financial_tag'] != 171)
& (dt1['financial_tag'] != 172)]
b = dt2.loc[(dt2['financial_tag'] != 157)
& (dt2['financial_tag'] != 171)
& (dt2['financial_tag'] != 172)]
c = dt3.loc[(dt3['financial_tag'] != 157)
& (dt3['financial_tag'] != 171)
& (dt3['financial_tag'] != 172)]
a.to_csv('f:\hahSep.csv', encoding='gbk')
b.to_csv('f:\hahAug.csv', encoding='gbk')
c.to_csv('f:\hahJul.csv', encoding='gbk')
abc = pd.concat([a, b, c])
abc.to_csv('f:\hah.csv', encoding='gbk')
print('done')
hah.csv：
financial_tag
N有效971810
缺少9
hahAug.csv
financial_tag
N有效364144
缺少0
hahJul.csv
financial_tag
N有效356924
缺少0
hahSep.csv
financial_tag
N有效250751
缺少0