Unique values of two columns for pandas dataframe [duplicate]

Question

Suppose I have pandas data frame with 2 columns:

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:

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?

Answer 1

You need 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