how to create and append multiple rows using two loops in python

Question

i need to create a dataframe such that i have the output as follows

day hour cal_hr
1   6    106
1   7    107
1   8    108
..
..
1   24   124
..
7   1    701
7   2    702
..
..
7   24   724

i want to loop through day and then hour and then do a concat of day and hour. With preceding 0 for 106(say)

something like

for i in range(1,8):
    for j in range(6,25):
        df.append(i,j)
 df=pd.dataFrame(df)

can df.append create two variables simaltaneously

unfortunately i need to create a dataframe , so that i can merge it back with another table. Cal_hr can be create later on if i have day and hour created. coz it is just a concatenation of day and hour. id day = 1 and hour =6 then cal_hr = 106 and so on — Mukul
– Mukul, Commented Jul 23, 2016 at 16:33

score 4 · Accepted Answer · 2016-07-23 16:42:09Z

4

Append to a list then convert to a dataframe. It would be much more efficient.

df = pd.DataFrame([(i, j, 100*i+j) 
                    for i in range(1, 8) 
                    for j in range(6, 25)], 
                    columns=['day', 'hour', 'cal_hr'])

df.head()
Out[143]: 
   day  hour  cal_hr
0    1     6     106
1    1     7     107
2    1     8     108
3    1     9     109
4    1    10     110

df.tail()
Out[144]: 
     day  hour  cal_hr
128    7    20     720
129    7    21     721
130    7    22     722
131    7    23     723
132    7    24     724

edited Jul 23, 2016 at 16:42

answered Jul 23, 2016 at 16:33

user2285236

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2 Comments

Mukul Over a year ago

hi ayhan, can this logic be extended , say i want to add another column 'week' which goes from 201501 to 201552 and then 201601 to 201652, can i do the following ? core_hours = pd.DataFrame([(i, j, k, 100*i+j) for i in range(1, 8) for j in range(start_hour, end_hour+1) for k in range(201601, 201652)], columns = ['day', 'hour_i', 'week', 'hour']) but in that case how do i make the loop to restart from 1 when the week hits 201652 (say)

user2285236 Over a year ago

@Mukul Can you edit the example in your post to include the week column. I don't understand exactly.

piRSquared · Accepted Answer · 2016-07-24 02:19:13Z

0

This isn't as fast or as intuitive as @ayhan's answer, but I think it's an interesting way to think about it.

day = pd.Series(np.arange(1, 8), name='day')
hour = pd.Series(np.arange(6, 25), name='hour')
df = pd.DataFrame(np.add.outer(day * 100, hour), day, hour)
df = df.stack().rename('cal_hr').reset_index()

df.head()

df.tail()

answered Jul 24, 2016 at 2:19

piRSquared

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