Pandas Groupby唯一多列 [英] Pandas Groupby Unique Multiple Columns
本文介绍了Pandas Groupby唯一多列的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我有一个数据框.
import pandas as pd
df = pd.DataFrame(
{'number': [0,0,0,1,1,2,2,2,2], 'id1': [100,100,100,300,400,700,700,800,700], 'id2': [100,100,200,500,600,700,800,900,1000]})
id1 id2 number
0 100 100 0
1 100 100 0
2 100 200 0
3 300 500 1
4 400 600 1
5 700 700 2
6 700 800 2
7 800 900 2
8 700 1000 2
(这代表我正在使用的更大的数据帧〜数百万行).
(This represents a much larger dataframe I am working with ~millions of rows).
我可以将groupby().unique
应用于一列:
df.groupby(['number'])['id1'].unique()
number
0 [100]
1 [300, 400]
2 [700, 800]
Name: id1, dtype: object
df.groupby(['number'])['id2'].unique()
number
0 [100, 200]
1 [500, 600]
2 [700, 800, 900, 1000]
Name: id2, dtype: object
我想同时对两列进行唯一性处理,以使其在数据帧中排序:
I want to do the unique over both columns simultaneously to get it ordered in a dataframe:
number
0 [100, 200]
1 [300, 400, 500, 600]
2 [700, 800, 900, 1000]
当我尝试对两列进行此操作时,都会收到错误消息:
When I try and do this for both columns I get the error:
pd.Data.Frame(df.groupby(['number'])['id1', 'id2'].unique())
Traceback (most recent call last):
File "C:\Python34\lib\site-packages\IPython\core\interactiveshell.py", line 2885, in run_code
exec(code_obj, self.user_global_ns, self.user_ns)
File "<ipython-input-15-bfc6026e241e>", line 9, in <module>
df.groupby(['number'])['id1', 'id2'].unique()
File "C:\Python34\lib\site-packages\pandas\core\groupby.py", line 498, in __getattr__
(type(self).__name__, attr))
AttributeError: 'DataFrameGroupBy' object has no attribute 'unique'
怎么办?使用多索引是否更可取?
What do? Is it preferable to use a multi-index?
此外,还可以按如下方式获得输出:
In addition is it possible to get the output as follows:
number
0 100
0 200
1 300
1 400
1 500
1 600
2 700
2 800
2 900
2 1000
推荐答案
您可以通过[]
选择所有列:
You can select all column by []
:
s = (df.groupby(['number'])['id1', 'id2']
.apply(lambda x: pd.unique(x.values.ravel()).tolist()))
print (s)
number
0 [100, 200]
1 [300, 500, 400, 600]
2 [700, 800, 900, 1000]
dtype: object
或者:
s2 = (df.groupby(['number'])['id1', 'id2']
.apply(lambda x: np.unique(x.values.ravel()).tolist()))
print (s2)
number
0 [100, 200]
1 [300, 400, 500, 600]
2 [700, 800, 900, 1000]
dtype: object
如果需要将输出作为列,请首先通过 stack
,然后 drop_duplicates
:
If need output as column, first reshape by stack
and then drop_duplicates
:
df1 = (df.set_index('number')[['id1', 'id2']]
.stack()
.reset_index(level=1, drop=True)
.reset_index(name='a')
.drop_duplicates())
print (df1)
number a
0 0 100
5 0 200
6 1 300
7 1 500
8 1 400
9 1 600
10 2 700
13 2 800
15 2 900
17 2 1000
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