charles.sart...@gmail.com wrote:
> Hello there!
>
> I`m trying to group by a list of Row() objects in 12days interval and
> sum(). values. Here is an example of the list
>
> [Row(time=datetime.datetime(2013, 1, 1, 0, 0), sum=4676557380615),
> [Row(time=datetime.datetime(2013, 1, 2, 0, 0), sum=6549630855895),
> [Row(time=datetime.datetime(2013, 1, 3, 0, 0), sum=6549630855895), ...]
>
> Row() objects has two vars: row.time and row.sum
>
>
> The result that I`m looking for is:
> [[datetime.datetime(2013, 1, 1, 0, 0), value],
> [datetime.datetime(2013, 1, 12, 0, 0), value],
> [datetime.datetime(2013, 1, 24, 0, 0), value]
> ]
> Where value is the sum() of all row.sum in that interval.
>
> I`m trying to use itertools.groupby by I could not get it to work yet.
If the data is sorted by time then you can use groupby, otherwise consider
putting it into a (default)dict. Here is an example for both methods:
import datetime
import random
from itertools import groupby
from collections import defaultdict, namedtuple
BASEDATE = datetime.datetime(2015, 1, 1)
INTERVAL = 12 # time interval in days
DAYS = datetime.timedelta(days=INTERVAL)
def make_sample_rows():
random.seed(42)
Row = namedtuple("Row", "time sum")
return [
Row(BASEDATE + datetime.timedelta(days=random.randrange(-20, 80)),
random.randrange(300))
for i in range(30)]
def get_key(row):
offset = (row.time - BASEDATE).days // INTERVAL
return BASEDATE + datetime.timedelta(days=offset)
def format_time(time):
return time.strftime("%Y-%m-%d")
if __name__ == "__main__":
rows = make_sample_rows()
# with groupby()
for key, group in groupby(sorted(rows), key=get_key):
print("{} - {}".format(format_time(key), format_time(key+DAYS)))
print("-" * 23)
group = list(group)
for row in group:
print("{} {:4}".format(format_time(row.time), row.sum))
print("{:>15}".format("----"))
print("{:15}".format(sum(row.sum for row in group)))
print("")
# with defaultdict
d = defaultdict(int)
for row in rows:
d[get_key(row)] += row.sum
for time, sum in sorted(d.items()):
print("{} {:4}".format(format_time(time), sum))
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