How to join Date and Time of variable length using Pandas

Question

I have a fixed-length Time list:

time_list = ['21:00:00', '22:00:00', '23:00:00', '00:00:00', '01:00:00']

However, I have a long Date list:

date_list = 
['2019-07-09',
 '2019-07-09',
 '2019-07-09',
 '2019-07-09',
 '2019-07-09',
 '2019-07-09',
 '2019-07-09',
 '2019-07-10',
 '2019-07-10',
 '2019-07-10',
 '2019-07-10',
 '2019-07-08',
 '2019-07-08',
 '2019-07-08'
 ....
 ]

What I want to do is join date_list and time_list so the new df looks like this:

date_time =
['2019-07-09 21:00:00',
 '2019-07-09 22:00:00',
 '2019-07-09 23:00:00',
 '2019-07-09 00:00:00',
 '2019-07-09 01:00:00',
 '2019-07-09 21:00:00',
 '2019-07-09 22:00:00',
 '2019-07-10 23:00:00',
 '2019-07-10 00:00:00',
 '2019-07-10 01:00:00',
 '2019-07-10 21:00:00',
 '2019-07-08 22:00:00',
 '2019-07-08 23:00:00',
 '2019-07-08 00:00:00'
 ....
 ]

As you can see that the time_list is applied to date_list similar to one to one mapping. When the time_list runs out of value, it is repeated again but date_list is the same length and won't repeat.

What did I do?

I tried to do:

pd.MultiIndex.from_product([date_list, time_list]).map(' '.join).tolist()

But it does for each date_list joins time_list which gives extra values.

I also tried to do this but wont work:

[date_list  + " " + time_list]

Can you please help?

BENY · Accepted Answer · 2019-08-06 22:45:48Z

1

Try with

n=1+len(date_list)//len(time_list)
[x + ' ' +y for x , y in zip(date_list,(time_list*n)[:len(date_list)])]

Or we using the itertools.cycle

import itertools
[x+' '+y for x,y in zip(date_list, itertools.cycle(time_list))]

answered Aug 6, 2019 at 22:45

BENY

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Comments

adhg · Accepted Answer · 2019-08-07 00:38:19Z

On a very intuitive level I would simply have 2 for loops and a 'cyclical numerator' such that:

from collections import Counter

date_dict = Counter(date_list)
date_time = []
cyclical = 0

for d in date_dict:
    index = 0
    n = date_dict[d]
    for _ in range(n): 
        t = time_list[cyclical%len(time_list)]  
        cycle += 1
        date_time.append(d+" "+t)

desired result:

['2019-07-09 21:00:00',
 '2019-07-09 22:00:00',
 '2019-07-09 23:00:00',
 '2019-07-09 00:00:00',
 '2019-07-09 01:00:00',
 '2019-07-09 21:00:00',
 '2019-07-09 22:00:00',
 '2019-07-10 23:00:00',
 '2019-07-10 00:00:00',
 '2019-07-10 01:00:00',
 '2019-07-10 21:00:00',
 '2019-07-08 22:00:00',
 '2019-07-08 23:00:00',
 '2019-07-08 00:00:00']

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