python - Finding common elements between multiple dataframe columns

Question

Hope you could help me. I am new to python and pandas, so please bear with me. I am trying to find the common word between three data frames and I am using Jupiter Notebook.

Just for example:

df1=
A
dog
cat
cow 
duck
snake

df2=
A
pig
snail
bird
dog

df3=
A
eagle
dog 
snail
monkey

There is only one column in all data frames that is A. I would like to find

1. the common word among all columns
2. the words that are unique to their own columns and not in common.

Example:

duck is unique to df1, snail is unique to df2 and monkey is unique to df3.

I am using the below code to some use but not getting what I want straightforward,

df1[df1['A'].isin(df2['A']) & (df2['A']) & (df3['A'])]

Kindly let me know where I am going wrong. Cheers

Answer 1

Simplest way is to use set intersection

list(set(df1.A) & set(df2.A) & set(df3.A))

['dog']

---

However if you have a long list of these things, I'd use reduce from functools. This same technique can be used with @c???s????'s use of np.intersect1d as well.

from functools import reduce

list(reduce(set.intersection, map(set, [df1.A, df2.A, df3.A])))

['dog']