Find equal columns between two dataframes

Question

I have two pandas data frames, a and b:

a1   a2   a3   a4   a5   a6   a7
1    3    4    5    3    4    5
0    2    0           


        

Answer 1

dictionary comprehensions

Use a tuple of the column values as the hashable key in a dictionary

d = {(*t,): c for c, t in df2.items()}
{c: d[(*t,)] for c, t in df1.items()}

{'a1': 'b5',
 'a2': 'b7',
 'a3': 'b6',
 'a4': 'b4',
 'a5': 'b1',
 'a6': 'b3',
 'a7': 'b2'}

Just in case we don't have perfect representation, I've only produced the dictionary for columns where there is a match.

d2 = {(*t,): c for c, t in df2.items()}
d1 = {(*t,): c for c, t in df1.items()}

{d1[c]: d2[c] for c in {*d1} & {*d2}}

{'a5': 'b1',
 'a2': 'b7',
 'a7': 'b2',
 'a6': 'b3',
 'a3': 'b6',
 'a1': 'b5',
 'a4': 'b4'}

---

idxmax

This borders on the absurd... Don't actually do this.

{c: df2.T.eq(df1[c]).sum(1).idxmax() for c in df1}

{'a1': 'b5',
 'a2': 'b7',
 'a3': 'b6',
 'a4': 'b4',
 'a5': 'b1',
 'a6': 'b3',
 'a7': 'b2'}