我使用熊猫作为数据库替代品，因为我有多个数据库(Oracle, SQL Server等)，我无法使一个SQL等量命令序列。
我有一个表加载在一个DataFrame与一些列:
YEARMONTH, CLIENTCODE, SIZE, etc., etc.
在SQL中，计算每年不同客户端的数量将是:
SELECT count(distinct CLIENTCODE) FROM table GROUP BY YEARMONTH;
结果就是
201301 5000
201302 13245
我如何在熊猫中做到这一点?
当前回答
To obtain the number of different clients and sizes per year (i.e. number of unique values of multiple columns), use a list of columns: df.groupby('YEARMONTH')[['CLIENTCODE', 'SIZE']].nunique() Actually, the result from the above code can be obtained using SQL syntax on df using pandasql (a module built on pandas that lets you query pandas DataFrames using SQL syntax). #! pip install pandasql from pandasql import sqldf sqldf(""" SELECT COUNT(DISTINCT CLIENTCODE), COUNT(DISTINCT SIZE) FROM df GROUP BY YEARMONTH """) If you want to keep YEARMONTH as a column, i.e. the analog of the following SQL query SELECT YEARMONTH, COUNT(DISTINCT CLIENTCODE), COUNT(DISTINCT SIZE) FROM df GROUP BY YEARMONTH in pandas is the following (set as_index to False): df.groupby('YEARMONTH', as_index=False)[['CLIENTCODE', 'SIZE']].nunique() If you need to set custom names to the aggregated columns, i.e. the analog of the following SQL query: SELECT YEARMONTH, COUNT(DISTINCT CLIENTCODE) AS `No. clients`, COUNT(DISTINCT SIZE) AS `No. size` FROM df GROUP BY YEARMONTH use named aggregation in pandas: ( df.groupby('YEARMONTH', as_index=False) .agg(**{'No. clients':('CLIENTCODE', 'nunique'), 'No. size':('SIZE', 'nunique')}) )
其他回答
不同的列以及其他列上的聚合
要获得任何列(在您的例子中是CLIENTCODE)的不同值数量，我们可以使用nunique。我们可以在agg函数中传递输入作为字典，以及其他列上的聚合:
grp_df = df.groupby('YEARMONTH').agg({'CLIENTCODE': ['nunique'],
'other_col_1': ['sum', 'count']})
# to flatten the multi-level columns
grp_df.columns = ["_".join(col).strip() for col in grp_df.columns.values]
# if you wish to reset the index
grp_df.reset_index(inplace=True)
这里有一种方法可以使多个列上的计数不同。让我们看一些数据:
data = {'CLIENT_CODE':[1,1,2,1,2,2,3],
'YEAR_MONTH':[201301,201301,201301,201302,201302,201302,201302],
'PRODUCT_CODE': [100,150,220,400,50,80,100]
}
table = pd.DataFrame(data)
table
CLIENT_CODE YEAR_MONTH PRODUCT_CODE
0 1 201301 100
1 1 201301 150
2 2 201301 220
3 1 201302 400
4 2 201302 50
5 2 201302 80
6 3 201302 100
现在，列出感兴趣的列，并在稍微修改的语法中使用groupby:
columns = ['YEAR_MONTH', 'PRODUCT_CODE']
table[columns].groupby(table['CLIENT_CODE']).nunique()
我们获得:
YEAR_MONTH PRODUCT_CODE CLIENT_CODE
1 2 3
2 2 3
3 1 1
我相信这就是你想要的:
table.groupby('YEARMONTH').CLIENTCODE.nunique()
例子:
In [2]: table
Out[2]:
CLIENTCODE YEARMONTH
0 1 201301
1 1 201301
2 2 201301
3 1 201302
4 2 201302
5 2 201302
6 3 201302
In [3]: table.groupby('YEARMONTH').CLIENTCODE.nunique()
Out[3]:
YEARMONTH
201301 2
201302 3
有趣的是，len(unique())通常比nunique()快几倍(3 -15倍)。
创建一个数据透视表并使用非唯一级数函数:
ID = [ 123, 123, 123, 456, 456, 456, 456, 789, 789]
domain = ['vk.com', 'vk.com', 'twitter.com', 'vk.com', 'facebook.com',
'vk.com', 'google.com', 'twitter.com', 'vk.com']
df = pd.DataFrame({'id':ID, 'domain':domain})
fp = pd.pivot_table(data=df, index='domain', aggfunc=pd.Series.nunique)
print(fp)
输出:
id
domain
facebook.com 1
google.com 1
twitter.com 2
vk.com 3
