
This code imports the pandas library, reads an Excel file named "input.xlsx" into a pandas dataframe called "df". It then creates an empty dictionary called "columns_dict" to store the unique column names and their corresponding data.

Next, it loops through each column in the dataframe, gets the unique land use codes in the column, and concatenates them in alphabetical order to create a key for the dictionary. It checks whether the key already exists in the dictionary, and if so, appends the column data to the existing value. Otherwise, it creates a new key-value pair in the dictionary.

The code then creates a new dataframe called "new_df" from the dictionary, adds the first column from the original dataframe to the new dataframe, and saves the new dataframe to a new Excel file called "output.xlsx" without the index column.