Not able to assign values to a column. Bag_of_words

Question

I am trying to assign values to a column in my pandas df, however I am getting a blank column, here's the code:

df['Bag_of_words'] = ''
columns = ['genre', 'director', 'actors', 'key_words']


for index, row in df.iterrows():
    words = ''
    for col in columns:
        words += ' '.join(row[col]) + ' '
    row['Bag_of_words'] =words

The output is an empty column, can someone please help me understand what is happening here, as I am not getting any errors.

Answer 1

from the iterrows documentation:

2. You should never modify something you are iterating over. This is not guaranteed to work in all cases. Depending on the data types, the iterator returns a copy and not a view, and writing to it will have no effect.

So you do row[...] = ... and it turns out row is a copy and that's not affecting the original rows.

iterrows is frowned upon anyway, so you can instead

• join each words list per row to become strings

• aggregate those strings with " ".join row-wise

• add space to them

df["Bag_of_words"] = (df[columns].apply(lambda col: col.str.join(" "))
                                 .agg(" ".join, axis="columns")
                                 .add(" "))