如何在带有小时列的Pandas数据框中“丰富”每条记录？

Question

I have some dataframe in Pandas:

 1   2
 a  .2
 a  .3
 b  .5

I would like to add, for each of those records, a column with hour (from 0 to 23), so it will look like

 1   2    3
 a  .2    0
 a  .2    1
 a  .2    2
...
 a  .2   23
 a  .3    0
 a  .3    1
...
 a  .3   23
 b  .5    0
...
 b  .5   23

Answer 1

Create the hours array:

import numpy as np
hours = np.tile(np.arange(24), len(df))

Repeat each record of df by 24 times:

df = df.loc[df.index.repeat(24)].reset_index(drop=True)

Assign the hours array as a new column to the data frame:

df[3] = hours

df.head()
#   1     2 3
#0  a   0.2 0
#1  a   0.2 1
#2  a   0.2 2
#3  a   0.2 3
#4  a   0.2 4

---

Put together:

def expand_hours(df):
    import numpy as np
    hours = np.tile(np.arange(24), len(df))
    df = df.loc[df.index.repeat(24)].reset_index(drop=True)
    df[3] = hours
    return df

Answer 2

If your DataFrame is called df try this:

df['hour'] = Series(np.random.randint(0,24), index=df.index)

This should add a column with name 'hour' filled with integers generated between 0 and 23.