data loss with append pandas code example
Example 1: pandas left join
df.merge(df2, left_on = "doc_id", right_on = "doc_num", how = "left")
Example 2: combining 2 dataframes pandas
df_3 = pd.concat([df_1, df_2])
df.merge(df2, left_on = "doc_id", right_on = "doc_num", how = "left")
df_3 = pd.concat([df_1, df_2])