Get the total value per month in Python Dictionary where Key is DateTime object and Value is list of numbers

Question

I have a Python Dictionary where my key is a DateTime object and my Values are a list of numbers.

It looks like this:

I'm trying to get the total values per month based on the key, so if the key includes "09" as month then September will have 6 values.

I'm relatively new to Python and unsure on what would be the best approach for this, so far I have come up with something like this but I think I'm approaching it wrong:

if dictionary.keys() == re.search([0-9]{4}-(09)-[0-9]{2}):
    september.append(dictionary.value())
    total = len(september)
elif dictionary.keys() == re.search([0-9]{4}-(10)-[0-9]{2}):
    october.append(dictionary.value())
    total = len(october)

The dictionary:

{datetime.date(2020, 9, 16): [20412], datetime.date(2020, 9, 23): [20424], datetime.date(2020, 9, 30): [20427, 20431, 20428], datetime.date(2020, 10, 6): [20435], datetime.date(2020, 10, 8): [20447], datetime.date(2020, 10, 7): [20448, 20444, 20442, 20441], datetime.date(2020, 10, 5): [20434, 20436], datetime.date(2020, 10, 13): [20454, 20453], datetime.date(2020, 10, 14): [20459, 20463, 20462], datetime.date(2020, 10, 19): [20467, 20470, 20465], datetime.date(2020, 9, 28): [20429], datetime.date(2020, 10, 12): [20450], datetime.date(2020, 10, 28): [20478, 20480, 20479], datetime.date(2020, 10, 27): [20481], datetime.date(2020, 10, 20): [20468], datetime.date(2020, 11, 3): [20490, 20485, 20486], datetime.date(2020, 11, 5): [20491], datetime.date(2020, 11, 4): [20487], datetime.date(2020, 11, 11): [20494, 20495, 20499], datetime.date(2020, 11, 13): [20502], datetime.date(2020, 11, 12): [20500], datetime.date(2020, 11, 25): [20522, 20533, 20535, 20526, 20528, 20523], datetime.date(2020, 11, 19): [20514], datetime.date(2020, 11, 16): [20505], datetime.date(2020, 11, 18): [20508, 20519], datetime.date(2020, 12, 9): [20560, 20559], datetime.date(2020, 12, 11): [20562, 20561], datetime.date(2020, 12, 3): [20554, 20553, 20552], datetime.date(2020, 12, 2): [20542, 20546, 20551], datetime.date(2020, 11, 27): [20534], datetime.date(2020, 11, 23): [20525, 20524], datetime.date(2020, 11, 17): [20507], datetime.date(2020, 12, 16): [20569], datetime.date(2020, 12, 22): [20594, 20591, 20592, 20600, 20612, 20589], datetime.date(2021, 1, 6): [215, 214], datetime.date(2020, 12, 14): [20567], datetime.date(2020, 12, 23): [20606, 20604, 20607, 20585], datetime.date(2020, 12, 21): [20587], datetime.date(2021, 1, 21): [2110, 2114], datetime.date(2021, 1, 20): [2116], datetime.date(2021, 1, 27): [2133, 2125, 2126, 2129, 2134, 2130, 2122], datetime.date(2021, 1, 26): [2128], datetime.date(2021, 2, 8): [2150], datetime.date(2021, 2, 3): [2142, 2146], datetime.date(2021, 2, 17): [2170, 2164, 2166], datetime.date(2021, 2, 11): [2156, 2157], datetime.date(2021, 2, 5): [2147], datetime.date(2021, 1, 28): [2132], datetime.date(2021, 2, 15): [2160, 2161], datetime.date(2021, 1, 14): [217], datetime.date(2021, 2, 10): [2154], datetime.date(2021, 2, 18): [2174], datetime.date(2021, 3, 3): [21121, 21120, 21119, 21112], datetime.date(2021, 2, 24): [2193], datetime.date(2021, 2, 19): [2184], datetime.date(2021, 2, 25): [2199], datetime.date(2021, 3, 1): [21103], datetime.date(2021, 3, 10): [21130, 21138, 21142, 21136, 21137], datetime.date(2021, 3, 12): [21135, 21134], datetime.date(2021, 3, 18): [21156, 21145], datetime.date(2021, 3, 2): [21105], datetime.date(2021, 3, 16): [21144, 21163, 21154, 21155, 21158], datetime.date(2021, 3, 15): [21150, 21148], datetime.date(2021, 3, 19): [21159, 21161, 21160], datetime.date(2021, 3, 30): [21184, 21179], datetime.date(2021, 3, 31): [21182, 21187, 21188], datetime.date(2021, 3, 29): [21177], datetime.date(2021, 3, 26): [21174], datetime.date(2021, 3, 24): [21166, 21169], datetime.date(2021, 3, 22): [21164], datetime.date(2021, 4, 1): [21189], datetime.date(2021, 4, 7): [21200, 21203, 21195, 21198, 21193, 21202], datetime.date(2021, 3, 9): [21127], datetime.date(2021, 4, 12): [21209, 21207, 21210], datetime.date(2021, 4, 23): [21234, 21233], datetime.date(2021, 4, 21): [21231, 21230, 21232], datetime.date(2021, 4, 19): [21224, 21221, 21219], datetime.date(2021, 4, 20): [21227], datetime.date(2021, 4, 14): [21214, 21212, 21217, 21194, 21211, 21215], datetime.date(2021, 4, 28): [21240, 21243, 21245], datetime.date(2021, 4, 27): [21241, 21242], datetime.date(2021, 4, 29): [21250, 21247], datetime.date(2021, 4, 30): [21248], datetime.date(2021, 5, 5): [21254, 21253, 21255, 21259], datetime.date(2021, 5, 7): [21262], datetime.date(2021, 4, 6): [21197], datetime.date(2021, 5, 10): [21266, 21267], datetime.date(2021, 5, 12): [21268, 21269, 21271, 21273, 21277, 21278, 21275], datetime.date(2021, 5, 17): [21287, 21282, 21294], datetime.date(2021, 5, 19): [21289, 21292, 21293, 21290, 21283], datetime.date(2021, 5, 24): [21306, 21314, 21311, 21297, 21308], datetime.date(2021, 5, 25): [21300, 21300], datetime.date(2021, 5, 26): [21315, 21313, 21312, 21319, 21316, 21301, 21302, 21307], datetime.date(2021, 5, 27): [21320], datetime.date(2021, 6, 2): [21326, 21327, 21328, 21329, 21330], datetime.date(2021, 6, 1): [21323], datetime.date(2021, 6, 3): [21332, 21331, 21340], datetime.date(2021, 6, 9): [21347, 21341, 21344, 21348, 21349, 21355], datetime.date(2021, 6, 4): [21335, 21336, 21338, 21339], datetime.date(2021, 6, 10): [21352], datetime.date(2021, 6, 16): [21362, 21364, 21365], datetime.date(2021, 6, 15): [21371], datetime.date(2021, 6, 14): [21372], datetime.date(2021, 6, 21): [21380, 21385], datetime.date(2021, 6, 25): [21389], datetime.date(2021, 6, 30): [21406, 21408, 21411], datetime.date(2021, 6, 28): [21393, 21392], datetime.date(2021, 7, 1): [21391, 21412, 21413, 21409], datetime.date(2021, 6, 29): [21399, 21400], datetime.date(2021, 7, 7): [21423, 21426, 21424, 21427], datetime.date(2021, 7, 6): [21420, 21416], datetime.date(2021, 7, 5): [21417], datetime.date(2021, 7, 12): [21431, 21432], datetime.date(2021, 7, 14): [21438, 21429, 21442, 21446, 21445], datetime.date(2021, 7, 13): [21434], datetime.date(2021, 7, 21): [21451], datetime.date(2021, 7, 22): [21452, 21462], datetime.date(2021, 7, 19): [21464], datetime.date(2021, 7, 28): [21478, 21472, 21483, 21469, 21468, 21473, 21473, 21475], datetime.date(2021, 7, 29): [21480], datetime.date(2021, 8, 10): [21499, 21497], datetime.date(2021, 8, 13): [21506], datetime.date(2021, 8, 12): [21502], datetime.date(2021, 8, 9): [21500, 21498], datetime.date(2021, 8, 4): [21494, 21490, 21486], datetime.date(2021, 8, 11): [21505], datetime.date(2021, 8, 3): [21484], datetime.date(2021, 8, 6): [21488], datetime.date(2021, 8, 27): [21530, 21532, 21538, 21540], datetime.date(2021, 8, 20): [21524], datetime.date(2021, 8, 16): [21519], datetime.date(2021, 8, 24): [21533], datetime.date(2021, 8, 25): [21539, 21536], datetime.date(2021, 9, 1): [21550, 21549, 21545, 21547, 21541, 21543], datetime.date(2021, 8, 30): [21546], datetime.date(2021, 9, 8): [21554, 21555], datetime.date(2021, 9, 10): [21559]}

Answer 1

Note that even though you said, if you 9 should have 6 as a value, that's only for 2020 because there is a 2021.09 too. So it seems right to make the output dictionary keys year-month pairs.

Then are a couple of ways. If you want to get the number of values for each year-month pair, you can use dict.get method:

out = {}
for k,v in dct.items():
    out[(k.year, k.month)] = out.get((k.year, k.month), 0) + len(v)

or dict.setdefault method:

out = {}
for k,v in dct.items():
    out.setdefault((k.year, k.month), 0)
    out[(k.year, k.month)] += len(v)

Output:

>>> out[(2020, 9)]

6

---

But if you want to get all items in each year-month pair, you can use the same methods by slightly tweaking.

out = {}
for k,v in dct.items():
    out[(k.year, k.month)] = out.get((k.year, k.month), []) + v

or dict.setdefault method:

out = {}
for k,v in dct.items():
    out.setdefault((k.year, k.month), []).extend(v)

Then output:

>>> out[(2020, 9)]

[20412, 20424, 20427, 20431, 20428, 20429]