How to create a nested list conditioned on a parameter in python

Question

I have generated a day-wise nested list and want to calculate total duration between login and logout sessions and store that value individually in a duration nested list, organized by the day in which the login happened.

My python script is:

import datetime
import itertools

Logintime = [
        datetime.datetime(2021,1,1,8,10,10), 
        datetime.datetime(2021,1,1,10,25,19),
        datetime.datetime(2021,1,2,8,15,10),
        datetime.datetime(2021,1,2,9,35,10)
        ]
Logouttime = [
        datetime.datetime(2021,1,1,10,10,11),
        datetime.datetime(2021,1,1,17,0,10), 
        datetime.datetime(2021,1,2,9,30,10),
        datetime.datetime(2021,1,2,17,30,12) 
       
        ]

Logintimedaywise = [list(group) for k, group in itertools.groupby(Logintime,
                                                   key=datetime.datetime.toordinal)]
Logouttimedaywise = [list(group) for j, group in itertools.groupby(Logouttime,
                                                   key=datetime.datetime.toordinal)]
print(Logintimedaywise)
print(Logouttimedaywise)

# calculate total duration 
temp = []
l = []
for p,q in zip(Logintimedaywise,Logouttimedaywise):
        for a,b in zip(p, q):
                tdelta = (b-a) 
                diff = int(tdelta.total_seconds())  / 3600 
                if diff not in temp:
                        temp.append(diff)
l.append(temp)
print(l)

this script generating the following output (the duration in variable l is coming out as a flat list inside a singleton list):

[[datetime.datetime(2021, 1, 1, 8, 10, 10), datetime.datetime(2021, 1, 1, 10, 25, 19)], [datetime.datetime(2021, 1, 2, 8, 15, 10), datetime.datetime(2021, 1, 2, 9, 35, 10)]]

[[datetime.datetime(2021, 1, 1, 10, 10, 11), datetime.datetime(2021, 1, 1, 17, 0, 10)], [datetime.datetime(2021, 1, 2, 9, 30, 10), datetime.datetime(2021, 1, 2, 17, 30, 12)]]

[[2.000277777777778, 6.5808333333333335, 1.25, 7.917222222222223]]

But my desired output format is the following nested list of durations (each item in the list should be the list of durations for a given login day):

[[2.000277777777778, 6.5808333333333335] , [1.25, 7.917222222222223]]

anyone can help how can i store total duration as a nested list according to the login day?

thanks in advance.

What if login and logout are in different days? Then some inner lists of logintimedaywise and logouttimedaywise would have different number of elements, and your script would break... I'd first take the duration (logout - login), then sort the resulting list as a nested list organized according to only the login day — Girardi
– Girardi, Commented Feb 10, 2021 at 9:12

U13-Forward · Accepted Answer · 2021-02-10 09:02:05Z

Try changing this peace of code:

# calculate total duration 
temp = []
l = []
for p,q in zip(Logintimedaywise,Logouttimedaywise):
        for a,b in zip(p, q):
                tdelta = (b-a) 
                diff = int(tdelta.total_seconds())  / 3600 
                if diff not in temp:
                        temp.append(diff)
l.append(temp)
print(l)

To:

# calculate total duration 
l = []
for p,q in zip(Logintimedaywise,Logouttimedaywise):
        l.append([])
        for a,b in zip(p, q):
                tdelta = (b-a) 
                diff = int(tdelta.total_seconds())  / 3600 
                if diff not in l[-1]:
                        l[-1].append(diff)
print(l)

Then the output would be:

[[datetime.datetime(2021, 1, 1, 8, 10, 10), datetime.datetime(2021, 1, 1, 10, 25, 19)], [datetime.datetime(2021, 1, 2, 8, 15, 10), datetime.datetime(2021, 1, 2, 9, 35, 10)]]
[[datetime.datetime(2021, 1, 1, 10, 10, 11), datetime.datetime(2021, 1, 1, 17, 0, 10)], [datetime.datetime(2021, 1, 2, 9, 30, 10), datetime.datetime(2021, 1, 2, 17, 30, 12)]]
[[2.000277777777778, 6.5808333333333335], [1.25, 7.917222222222223]]

I add a new sublist for every iteration.

Girardi · Accepted Answer · 2021-02-10 18:44:59Z

Your solution and the answer by @U11-Forward will break if login and logout for the same session happen in different days, since the inner lists in Logintimedaywise and Logouttimedaywise will have different number of elements.

To avoid that, a way simpler solution is if you first calculate the duration for all pairs of login, logout, then you create the nested lists based only on the login day (or logout day if you wish), like this:

import datetime
import itertools
import numpy

# define the login and logout times
Logintime = [datetime.datetime(2021,1,1,8,10,10),datetime.datetime(2021,1,1,10,25,19),datetime.datetime(2021,1,2,8,15,10),datetime.datetime(2021,1,2,9,35,10)]
Logouttime = [datetime.datetime(2021,1,1,10,10,11),datetime.datetime(2021,1,1,17,0,10), datetime.datetime(2021,1,2,9,30,10),datetime.datetime(2021,1,2,17,30,12) ] 

# calculate the duration and the unique days in the set
duration = [ int((logout - login).total_seconds())/3600 for login,logout in zip(Logintime,Logouttime) ]
login_days = numpy.unique([login.day for login in Logintime])

# create the nested list of durations
# each inner list correspond to a unique login day
Logintimedaywise =  [[ login for login in Logintime if login.day == day ] for day in login_days ]
Logouttimedaywise = [[ logout for login,logout in zip(Logintime,Logouttime) if login.day == day ] for day in login_days ]
duration_daywise = [[ d for d,login in zip(duration,Logintime) if login.day == day ] for day in login_days ]

# check
print(Logintimedaywise)
print(Logouttimedaywise)
print(duration_daywise)

Outputs

[[datetime.datetime(2021, 1, 1, 8, 10, 10), datetime.datetime(2021, 1, 1, 10, 25, 19)], [datetime.datetime(2021, 1, 2, 8, 15, 10), datetime.datetime(2021, 1, 2, 9, 35, 10)]]
[[datetime.datetime(2021, 1, 1, 10, 10, 11), datetime.datetime(2021, 1, 1, 17, 0, 10)], [datetime.datetime(2021, 1, 2, 9, 30, 10), datetime.datetime(2021, 1, 2, 17, 30, 12)]]
[[2.000277777777778, 6.5808333333333335], [1.25, 7.917222222222223]]

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