How to remove a pandas dataframe from another data

Question

How to remove a pandas dataframe from another dataframe, just like the set subtraction:

a=[1,2,3,4,5]
b=[1,5]
a-b=[2,3,4]

And now we have two pandas dataframe, how to remove df2 from df1:

In [5]: df1=pd.DataFrame([[1,2],[3,4],[5,6]],columns=['a','b'])
In [6]: df1
Out[6]:
   a  b
0  1  2
1  3  4
2  5  6


In [9]: df2=pd.DataFrame([[1,2],[5,6]],columns=['a','b'])
In [10]: df2
Out[10]:
   a  b
0  1  2
1  5  6

Then we expect df1-df2 result will be:

In [14]: df
Out[14]:
   a  b
0  3  4

How to do it?

Thank you.

Answer 1

A set logic approach. Turn the rows of df1 and df2 into sets. Then use set subtraction to define new DataFrame

idx1 = set(df1.set_index(['a', 'b']).index)
idx2 = set(df2.set_index(['a', 'b']).index)

pd.DataFrame(list(idx1 - idx2), columns=df1.columns)

   a  b
0  3  4