How to compare an objects in a list to another object that is in the same list?

Question

nrmcdate is a list in an order of name, class, and date. This list represents the class the student did not attend and the date which the student did not attend. eg (john, 5537, datetime.datetime(2021, 5, 15, 0, 0)) means john did not attend class 5537 at 15-5-2021

registered_lists is the list of student that have registered to that class. So in this list there will be repeating names. eg. ('JOHN', 5537), ('JOHN', 5620) means john has registered to class 5620 and 5537.

nrmcdate = [
    ('JOHN', 5537, datetime.datetime(2021, 5, 15, 0, 0)),
    ('JOHN', 5620, datetime.datetime(2021, 5, 15, 0, 0)),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5537, datetime.datetime(2021, 8, 3, 0, 0)),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5537, datetime.datetime(2021, 8, 10, 0, 0)),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5558, datetime.datetime(2021, 8, 12, 0, 0)),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5563, datetime.datetime(2021, 8, 12, 0, 0)),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5628, datetime.datetime(2021, 5, 20, 0, 0)),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5628, datetime.datetime(2021, 7, 8, 0, 0)),
    ("['ASAZPGXWZKSWKZBASJQZCI']", 5531, datetime.datetime(2021, 5, 7, 0, 0)),
    ("['ASAZPGXWZKSWKZBASJQZCI']", 5531, datetime.datetime(2021, 5, 14, 0, 0)),
    ("['KSPKGRMQSNSO']", 5558, datetime.datetime(2021, 5, 11, 0, 0)),
    ("['KSPKGRMQSNSO']", 5558, datetime.datetime(2021, 6, 3, 0, 0)),
    ("['KSPKGRMQSNSO']", 5558, datetime.datetime(2021, 7, 8, 0, 0)),
    ("['KSPKGRMQSNSO']", 5558, datetime.datetime(2021, 7, 15, 0, 0)),
    ("['KSPKGRMQSNSO']", 5558, datetime.datetime(2021, 7, 30, 0, 0)),
    ("['NSPZOPGXWZTEWQZPSHZKSJIZK']", 5530, datetime.datetime(2021, 5, 7, 0, 0)),
    ("['NSPZOPGXWZTEWQZPSHZKSJIZK']", 5530, datetime.datetime(2021, 7, 9, 0, 0)),
    ("['NSPZOPGXWZTEWQZPSHZKSJIZK']", 5530, datetime.datetime(2021, 7, 16, 0, 0)),
    ("['NSPZOPGXWZTEWQZPSHZKSJIZK']", 5530, datetime.datetime(2021, 8, 6, 0, 0)),
    ("['NSPZOPGXWZTEWQZPSHZKSJIZK']", 5540, datetime.datetime(2021, 4, 28, 0, 0)),
    ("['NSPZOPGXWZTEWQZPSHZKSJIZK']", 5540, datetime.datetime(2021, 8, 11, 0, 0)),
    ("['NSPZOPGXWZTEWQZPSHZKSJIZK']", 5541, datetime.datetime(2021, 4, 27, 0, 0)),
    ("['NSPZOPGXWZTEWQZPSHZKSJIZK']", 5541, datetime.datetime(2021, 5, 7, 0, 0)),
    ("['NSPZOPGXWZTEWQZPSHZKSJIZK']", 5541, datetime.datetime(2021, 5, 28, 0, 0)),
    ("['NSPZOPGXWZTEWQZPSHZKSJIZK']", 5546, datetime.datetime(2021, 5, 6, 0, 0)),
    ("['NZAZJPGXWZTEKSWKZOSZKZAJZV']", 5531, datetime.datetime(2021, 5, 14, 0, 0)),
    ("['NZAZJPGXWZTEKSWKZOSZKZAJZV']", 5532, datetime.datetime(2021, 6, 3, 0, 0)),
    ("['NZAZJPGXWZTEKSWKZOSZKZAJZV']", 5532, datetime.datetime(2021, 7, 15, 0, 0)),
    ("['NZAZJPGXWZTEKSWKZOSZKZAJZV']", 5535, datetime.datetime(2021, 5, 21, 0, 0)),
    ("['NZAZJPGXWZTEKSWKZOSZKZAJZV']", 5556, datetime.datetime(2021, 7, 13, 0, 0)),
    ("['NZAZJPGXWZTEKSWKZOSZKZAJZV']", 5561, datetime.datetime(2021, 5, 11, 0, 0)),
    ("['NZAZJPGXWZTEKSWKZOSZKZAJZV']", 5561, datetime.datetime(2021, 6, 29, 0, 0)),
    ("['NZAZJPGXWZTEKSWKZOSZKZAJZV']", 5561, datetime.datetime(2021, 7, 13, 0, 0)),
    ("['NZAZJPGXWZTEKSWKZOSZKZAJZV']", 5620, datetime.datetime(2021, 7, 30, 0, 0)),
    ("['NZAZJPGXWZTEKSWKZOSZKZAJZV']", 5626, datetime.datetime(2021, 7, 15, 0, 0)),
    ("['NZAZJPGXWZTEKSWKZOSZKZAJZV']", 5643, datetime.datetime(2021, 6, 29, 0, 0)),
    ("['NZAZJPGXWZTEKSWKZOSZKZAJZV']", 5643, datetime.datetime(2021, 8, 10, 0, 0)),
    # Many more rows...
]

and

registered_list = [
    ('JOHN', 5537),
    ('JOHN', 5620),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5531),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5534),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5537),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5554),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5558),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5563),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5620),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5624),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5628),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5631),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5632),
    ('["KSXXGPSPZQWTS\'SVZCIXZOOZQGO"]', 5635),
    ('["KZGD\'GPUKJTQEZTQ"]', 5618),
    ("['ASAZPGXWZKSWKZBASJQZCI']", 5531),
    ("['ASAZPGXWZKSWKZBASJQZCI']", 5533),
    ("['ASAZPGXWZKSWKZBASJQZCI']", 5536),
    ("['ASAZPGXWZKSWKZBASJQZCI']", 5542),
    ("['ASAZPGXWZKSWKZBASJQZCI']", 5544),
    ("['ASAZPGXWZKSWKZBASJQZCI']", 5548),
    ("['ASAZPGXWZKSWKZBASJQZCI']", 5554),
    ("['ASAZPGXWZKSWKZBASJQZCI']", 5557),
    ("['ASAZPGXWZKSWKZBASJQZCI']", 5562),
    ("['ASAZPGXWZKSWKZBASJQZCI']", 5620),
    ("['ASAZPGXWZKSWKZBASJQZCI']", 5623),
    ("['ASAZPGXWZKSWKZBASJQZCI']", 5627),
    ("['BZAZJGQEKSO']", 5643),
    ("['BZAZJGQEKSO']", 5645),
    ("['BZAZJGQEKSO']", 5647),
    ("['CEISJQY,UKSCKZSHUK']", 5530),
    ("['CEISJQY,UKSCKZSHUK']", 5554),
    ("['CEISJQY,UKSCKZSHUK']", 5559),
    ("['CEISJQY,UKSCKZSHUK']", 5564),
    ("['CEISJQY,UKSCKZSHUK']", 5598),
    ("['CEISJQY,UKSCKZSHUK']", 5599),
    ("['CEISJQY,UKSCKZSHUK']", 5642),
    ("['CZJ,SGJSZNQMI']", 5531),
    ("['CZJ,SGJSZNQMI']", 5533),
    ("['CZJ,SGJSZNQMI']", 5536),
    ("['CZJ,SGJSZNQMI']", 5542),
    ("['CZJ,SGJSZNQMI']", 5544),
    ("['CZJ,SGJSZNQMI']", 5548),
    ("['CZJ,SGJSZNQMI']", 5554),
    ("['CZJ,SGJSZNQMI']", 5557),
    ("['CZJ,SGJSZNQMI']", 5562),
    ("['CZJ,SGJSZNQMI']", 5620),
    ("['CZJ,SGJSZNQMI']", 5623),
    ("['CZJ,SGJSZNQMI']", 5627),
    ("['CZOJTQIKZE']", 5543),
    ("['CZOJTQIKZE']", 5547),
    ("['CZOJTQIKZE']", 5551),
    ("['CZOJTQIKZE']", 5555),
    ("['UKZSDSHQMU']", 5626),
    ("['UKZSDSHQMU']", 5643),
    ("['UKZSDSHQMU']", 5644),
    ("['UKZSDSHQMU']", 5646),
    ("['VOPZOZRM/IOSIZVXTOZQMO']", 5538),
    ("['VOPZOZRM/IOSIZVXTOZQMO']", 5540),
    ("['VOPZOZRM/IOSIZVXTOZQMO']", 5541),
    ("['VOPZOZRM/IOSIZVXTOZQMO']", 5620),
    ("['VOPZOZRM/IOSIZVXTOZQMO']", 5624),
    ("['VOPZOZRM/IOSIZVXTOZQMO']", 5626),
    ("['VOPZOZRM/IOSIZVXTOZQMO']", 5631),
    ("['VOPZOZRM/IOSIZVXTOZQMO']", 5633),
    ("['VOPZOZRM/IOSIZVXTOZQMO']", 5636),
    ("['VVSEZPXWZKSWSJESVXZOOZQGO']", 5542),
    ("['VVSEZPXWZKSWSJESVXZOOZQGO']", 5544),
    ("['VVSEZPXWZKSWSJESVXZOOZQGO']", 5548),
    ("['VVSEZPXWZKSWSJESVXZOOZQGO']", 5555),
    ("['VVSEZPXWZKSWSJESVXZOOZQGO']", 5557),
    ("['ZSJZNZAXQMOWJSZQGAXZOOZQGO']", 5627)
]

Currently I am required to compare the dates of nrmcdate to itself and see if the dates are 3 days apart. eg.(not from the list above) [(Aang, 12, datetime.datetime(2021, 05, 15)),( Ben, 22, datetime.datetime(2021, 05, 12)] since the objects in the list is three days apart it will then take the name and compare to the registerd_lists. Once the two name have a match in the registered list, the programme will then check to see if Aang and Ben have a common class. output eg. (Aang, Ben , 16) this means Aang and Ben is in the same class 16.

I have been trying to figure out how to compare the dates for the past few weeks and i hope someone here could give a solution.

You could use nested loops to compare each pair of objects in the `nrmcdate` list to see if they are 3 days apart. This is not the most efficient solution. — zr0gravity7, Jan 05 '22 at 16:50
Please review my edit and try to include a minimum set of data that will illustrate your issue. — JonSG, Jan 05 '22 at 17:29
Does this answer your question? [Days between two dates?](https://stackoverflow.com/questions/8258432/days-between-two-dates) — JonSG, Jan 05 '22 at 17:32

score 0 · Accepted Answer · answered Jan 05 '22 at 19:57

I would start by listing all the pairs

itertools.combinations(nrmcdate, 2) # don't forget to import

Then for all pairs

def common_class(pair, registered):
    person1 = pair[0]
    person2 = pair[1]
    if (abs((person1[2] - person2[2]).days) >= 3): #check if 3 days apart
        if common_classes := set(registered[person1[0]]).intersection(registered[person2[0]]): # they have a common class
            return (person1[0], person2[0], common_classes)
    return None

at last convert registered_list to a dict using:

result_dict = {}
for x in registered_list:
    result_dict.setdefault(x[0], []).append(x[1])

then to put this all toghether:

import datetime
import itertools

nrmcdate = [("Aang", 12, datetime.datetime(2021, 5, 15)),( "Ben", 22, datetime.datetime(2021, 5, 12))]
registered_list = [('Ben', 5537), ('Aang', 5537)]

itertools.combinations(nrmcdate, 2)

def common_class(pair, registered):
    person1 = pair[0]
    person2 = pair[1]
    if (abs((person1[2] - person2[2]).days) >= 3): #check if 3 days apart
        if common_classes := set(registered[person1[0]]).intersection(registered[person2[0]]): # they have a common class
            return (person1[0], person2[0], common_classes)
    return None

result_dict = {}
for x in registered_list:
    result_dict.setdefault(x[0], []).append(x[1])

print([res for x in itertools.combinations(nrmcdate, 2) if (res := common_class(x, result_dict))]) # we at last check if the value is not none

I hope this works, it isn't really tested. For example if a name is in nrmcdate but not in registered_list, it would crash but it's not that hard to fix.

How to compare an objects in a list to another object that is in the same list?

1 Answers1