Some useful melt / pivot stuff for pandas DataFrames

pip install a-pandas-ex-melt-pivot-tools

from a_pandas_ex_melt_pivot_tools import pd_add_stack_melt_tools

pd_add_stack_melt_tools()

import pandas as pd

df = pd.DataFrame(

    {

        "A": ["foo", "foo", "foo", "foo", "foo", "bar", "bar", "bar", "bar"],

        "B": ["one", "one", "one", "two", "two", "one", "one", "two", "two"],

        "C": [

            "small",

            "large",

            "large",

            "small",

            "small",

            "large",

            "small",

            "small",

            "large",

        ],

        "D": [1, 2, 2, 3, 3, 4, 5, 6, 7],

        "E": [2, 4, 5, 5, 6, 6, 8, 9, 9],

    }

)

print('___________________________________')

print(f'{df}\n\n')

print('___________________________________')

print(f"{df.ds_pivot_to_list(columns=['A'])}\n\n")

print(f"{df.ds_pivot_to_list(columns=['A','B'])}\n\n")

print(f"{df.ds_pivot_to_list(columns=['A','B', 'C'],stack=True)}\n\n")

print(f"{df.ds_pivot_to_list_no_old_index_column(columns=['A'])}\n\n")

print(f"{df.ds_pivot_to_list_no_old_index_column(columns=['A','B'])}\n\n")

print(f"{df.ds_pivot_to_list_no_old_index_column(columns=['A','B', 'C'],stack=True)}\n\n")

print(f"{df.ds_pivot_to_list_no_old_index_column_transposed(columns=['A'],stack=True)}\n\n")

print(f"{df.ds_pivot_to_list_no_old_index_column_transposed(columns=['A','B'],stack=True)}\n\n")

print(f"{df.ds_pivot_to_list_no_old_index_column_transposed(columns=['A','B', 'C'],stack=True)}\n\n")

___________________________________

     A    B      C  D  E

0  foo  one  small  1  2

1  foo  one  large  2  4

2  foo  one  large  2  5

3  foo  two  small  3  5

4  foo  two  small  3  6

5  bar  one  large  4  6

6  bar  one  small  5  8

7  bar  two  small  6  9

8  bar  two  large  7  9

___________________________________

                                            bar  ...      old_columns

old_columns                                      ...                 

B                    [one, one, two, two, None]  ...  [B, B, B, B, B]

C            [large, small, small, large, None]  ...  [C, C, C, C, C]

D                            [4, 5, 6, 7, None]  ...  [D, D, D, D, D]

E                            [6, 8, 9, 9, None]  ...  [E, E, E, E, E]

[4 rows x 3 columns]

                              bar  ... old_columns

                              one  ...            

old_columns                        ...            

C            [large, small, None]  ...   [C, C, C]

D                    [4, 5, None]  ...   [D, D, D]

E                    [6, 8, None]  ...   [E, E, E]

[3 rows x 5 columns]

                         bar                   foo         old_columns

                         one        two        one     two            

old_columns                                                           

D                        NaN        NaN        NaN     NaN      [D, D]

            large  [4, None]  [7, None]     [2, 2]     NaN         NaN

            small  [5, None]  [6, None]  [1, None]  [3, 3]         NaN

E                        NaN        NaN        NaN     NaN      [E, E]

            large  [6, None]  [9, None]     [4, 5]     NaN         NaN

            small  [8, None]  [9, None]  [2, None]  [5, 6]         NaN

                            bar                                  foo

B          [one, one, two, two]            [one, one, one, two, two]

C  [large, small, small, large]  [small, large, large, small, small]

D                  [4, 5, 6, 7]                      [1, 2, 2, 3, 3]

E                  [6, 8, 9, 9]                      [2, 4, 5, 5, 6]

              bar                                    foo                

              one             two                    one             two

C  [large, small]  [small, large]  [small, large, large]  [small, small]

D          [4, 5]          [6, 7]              [1, 2, 2]          [3, 3]

E          [6, 8]          [9, 9]              [2, 4, 5]          [5, 6]

         bar          foo        

         one  two     one     two

D large  [4]  [7]  [2, 2]     NaN

  small  [5]  [6]     [1]  [3, 3]

E large  [6]  [9]  [4, 5]     NaN

  small  [8]  [9]     [2]  [5, 6]

bar  B      one

     C    large

     D        4

     E        6

     B      one

          ...  

foo  E        5

     B      two

     C    small

     D        3

     E        6

Length: 3524, dtype: object

bar  one  C    large

          D        4

          E        6

          C    large

          D        4

               ...  

foo  two  D        3

          E        5

          C    small

          D        3

          E        6

Length: 153, dtype: object

bar  one  large  D    4

                 E    6

          small  D    5

                 E    8

     two  large  D    7

                 E    9

          small  D    6

                 E    9

foo  one  large  D    2

                 E    4

                 D    2

                 E    5

                 D    2

                 E    4

                 D    2

                 E    5

          small  D    1

                 E    2

     two  small  D    3

                 E    5

                 D    3

                 E    6

                 D    3

                 E    5

                 D    3

                 E    6

dtype: object