I have two DataFrames, table_of_concepts_df (the left one) and jobs_score_table_of_context_df (the right one) of the same dtype int64 as you can see in images.

But, after merging them, the type of columns from the right DataFrame changes to float64: merged_df = table_of_concepts_df.merge(jobs_score_table_of_context_df, how="left", left_index=True, right_index=True) merged_df.dropna(inplace=True).
I haven't found any explanation in the pandas documentation relative to this weird behavior.
Could someone can give me explanation on why ?
Thanks.
