Check if a value in one column is in a list in another column

Question

I have a pandas dataframe like this:

and I need to know if city appears in the list in citylist (ignoring case).

I've tried to use apply like this, but can't figure out the correct syntax:

df.apply(lambda x: x['city'].lower() in x['citylist'])

Answer 1

Pass param axis=1 to apply to iterate row-wise:

In [49]:

df[df.apply(lambda x: x['city'].lower() in x['citylist'], axis=1)]
Out[49]:
          city                         citylist
1       RESTON                [reston, herndon]
4  SPRINGFIELD  [springfield, west springfield]