Python pandas 数据框的两列的唯一值
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Unique values of two columns for pandas dataframe
提问by curious_one
Suppose I have pandas data frame with 2 columns:
假设我有 2 列的 Pandas 数据框：
df: Col1 Col2
1 1
1 2
1 2
1 2
3 4
3 4
Then I want to keep only the unique couple values (col1, col2) of these two columns and give their frequncy:
然后我只想保留这两列的唯一值（col1，col2）并给出它们的频率：
df2: Col1 Col2 Freq
1 1 1
1 2 3
3 4 2
I think to use df['Col1', 'Col2'].value_counts()but it works only for one column.
Does it exist a function to deal with many columns?
我想使用df['Col1', 'Col2'].value_counts()但它只适用于一列。是否存在处理多列的函数？
回答by jezrael
You need groupby+ size+ Series.reset_index:
你需要groupby+ size+ Series.reset_index：
df = df.groupby(['Col1', 'Col2']).size().reset_index(name='Freq')
print (df)
Col1 Col2 Freq
0 1 1 1
1 1 2 3
2 3 4 2
回答by Quickbeam2k1
You could try
你可以试试
df.groupby(['Col1', 'Col2']).size()
for a different visual output in comparison to jez's answer, you can extend that solution with
与 jez 的答案相比，对于不同的视觉输出，您可以扩展该解决方案
pd.DataFrame(df.groupby(['Col1', 'Col2']).size().rename('Freq'))
gives
给
Freq
Col1 Col2
1 1 1
2 3
3 4 2
