value_counts()是一种查看表格某列中有多少个不同值的快捷方法，并计算每个不同值有在该列中有多少重复值。
value_counts()是Series拥有的方法，一般在DataFrame中使用时，需要指定对哪一列或行使用

import pandas as pd
import numpy as np
filepath='C:\python\data_src\GFSCOFOG_03-05-2018 03-04-36-54_timeSeries\GFSCOFOG_CHA.csv'
data = pd.read_csv(filepath,encoding='utf-8')

数据样例如下图所示

查看Unit Name中有哪些不同的值，并计算每个值有多少个重复值

data['Unit Name'].value_counts()

data['Unit Name'].value_counts()
#输出
Percent of GDP                  3561
Domestic currency               3561
Percent of total expenditure     470
Name: Unit Name, dtype: int64

查看Sector Name中有哪些不同的值，并计算每个值有多少个重复值

data['Sector Name'].value_counts()

data['Sector Name'].value_counts()
#输出结果
Extrabudgetary central government                   1020
Social security funds                               1002
Central government (incl. social security funds)     944
Budgetary central government                         944
Local governments                                    944
General government                                   944
Central government (excl. social security funds)     944
State governments                                    850
Name: Sector Name, dtype: int64