Iterate through multiple columns in a Panda dataframe and find count unique values

Question

I am working with a dataset which looks like below:

I have imported this dataset to my code using the panda library. My goal is to find unique entries of the programming languages from columns 2, 3, 4. I wish the output to be:

    Python 4
    Perl 3
    C++ 3
....

Any leads would be helpful

Answer 1

Use DataFrame.filter with DataFrame.stack and Series.value_counts :

s = df.filter(like='Language').stack().value_counts()

Answer 2

This is an alternative way

df['lang1'].value_counts() + df['lang2'].value_counts() + df['lang3'].value_counts()

or

cols = ['lang1', 'lang2', 'lang2']
sum([df[col].value_counts() for col in cols])