Pandas Dataframe, add new column with range of data for each row in Python using Pandas

Question

I have a dataframe with a single column and want to create a new column called 'Hour' for hours 0-23 but for each row.

Current:

AN_LOG_ID
00000001
00000002
00000003

Desired output: (0-23 for each hour of the day for each row)

AN_LOG_ID    HOUR
00000001      0
00000001      1
...          ...
00000001      23
00000002      0
00000002      1
...          ...
00000002      23
00000003      0
00000003      1
...          ...
00000003      23

Answer 1

>>> df = df.assign(HOUR=[range(24)] * len(df)).explode("HOUR", ignore_index=True)
>>> df

   AN_LOG_ID HOUR
0   00000001    0
1   00000001    1
2   00000001    2
3   00000001    3
4   00000001    4
..       ...  ...
67  00000003   19
68  00000003   20
69  00000003   21
70  00000003   22
71  00000003   23

[72 rows x 2 columns]

Assign range(24) to each row as "HOUR" first, and then explode that "HOUR" column to spread hours on its own rows. (ignore_index=True makes the resultant index 0, 1, 2, ...)

Answer 2

We can use Index.repeat then use groupby.cumcount to get your HOUR column:

df = df.loc[df.index.repeat(24)]
df = df.assign(HOUR=df.groupby(level=0).cumcount()).reset_index(drop=True)

    N_LOG_ID  HOUR
0   00000001     0
1   00000001     1
2   00000001     2
3   00000001     3
4   00000001     4
..       ...   ...
67  00000003    19
68  00000003    20
69  00000003    21
70  00000003    22
71  00000003    23

Answer 3

Use a cross merge :

out = df.merge(pd.DataFrame({'HOUR': range(24)}), how='cross')

Output:

   AN_LOG_ID  HOUR
0   00000001     0
1   00000001     1
2   00000001     2
3   00000001     3
4   00000001     4
..       ...   ...
67  00000003    19
68  00000003    20
69  00000003    21
70  00000003    22
71  00000003    23

[72 rows x 2 columns]

Answer 4

Another possible solution, based on numpy :

pd.DataFrame(
    np.concatenate(
        (np.repeat(df.values, 24).reshape(-1,1),
         np.tile(np.arange(24), len(df)).reshape(-1,1)), axis=1), 
    columns=['AN_LOG_ID', 'HOUR'])

Output:

   AN_LOG_ID HOUR
0   00000001    0
1   00000001    1
2   00000001    2
3   00000001    3
4   00000001    4
..       ...  ...
67  00000003   19
68  00000003   20
69  00000003   21
70  00000003   22
71  00000003   23