unable to assign Null values to a Dataframe?

Question

I was working on a dataset where I found some null values. It's basically a Book Recommendation System. I have a column Author with author names with some null values. I used selenium to extract the Author's name using the Title. I stored the name in a list.

Now, I wish to enter these authors' names into my data frame, at the indexes where the actual column author is having null values.

Can anyone help me with this issue?

List b contains all the authors' names extracted using selenium. List nan contains indexes of the missing values of the Author column.

Answer 1

Assuming the author list is same length as missing values, you could zip through both lists for assignment:

for x, y in zip(authors_nan_indices, authors_list):
    book["Author"][x] = y

But in Pandas, aim for vectorized operations over looping:

book.loc[pd.isnull(book["Author"]), "Author"] = authors_list

Or with numpy.where using equality since NaN != NaN

book["Author"] = np.where(
    book["Author"] == book["Author"],
    book["Author"], 
    np.array(authors_list)
)