df = pd.DataFrame([10,20,30,40], index=[[1,1,2,2],[1,4,3,2]])
df.index.names=['a','b']
I would like to keep the rows in which index a equals index b:
0
1 1 10
2 2 40
I thought maybe a lambda could work in this case
df.index[lambda x: x[0]==x[1]]
but it doesn't. How could I get the result above?
May be something like below, where you can check if length of each multiindex set is 1:
df[df.index.map(lambda x: len(set(x)))==1]
0
a b
1 1 10
2 2 40
get_level_values will work for this
df[df.index.get_level_values(0)==df.index.get_level_values(1)]
Out[455]:
0
a b
1 1 10
2 2 40
To fix your code
df[df.index.map(lambda x: x[0]==x[1])]
Out[457]:
0
a b
1 1 10
2 2 40