Find the common columns between a list of Data frames

I want to find the common columns between a list of Data frames, the way that I started is, I defined x1 that is a lists of list ( for each data frames columns name), then I extract each sub list to a separate list.

I have the output as follows:

lst_1=['a1,a2,a3'] 

which has to be as follows, to be able to use set(lst_1) & set(lst_2)& etc :

lst_1=["a1","a2","a3"']

The code

x1=[]
dfs = [list of df]

for i, df in enumerate(dfs):
    x1.append([",".join((str(i) for i in df.columns))])

    globals()[f'lst_{i}']= x1[i]

>Solution :

reduce with set intersection

from functools import reduce

common = reduce(lambda a, b: set(a) & set(b), dfs)