How to select rows based categories in Pandas dataframe

Question

this is really trivial but can't believe I have wandered around for an hour and still can find the answer, so here you are:

    df = pd.DataFrame({"cats":["a","b"], "vals":[1,2]})
    df.cats = df.cats.astype("category")
    df

My problem is how to select the row that its "cats" columns's category is "a". I know that df.loc[df.cats == "a"] will work but it's based on equality on element. Is there a way to select based on levels of category?

Answer 1

This works:

df.cats[df.cats=='a']

UPDATE

The question was updated. New solution:

df[df.cats.cat.categories == ['a']]