Group together arbitrary date objects that are within a time range of each other

Question

I want to split the calendar into two-week intervals starting at 2008-May-5, or any arbitrary starting point.

So I start with several date objects:

Answer 1

Use itertools groupby with lambda function to divide by the length of period the distance from starting point.

>>> for i, group in groupby(range(30), lambda x: x // 7):
    print list(group)


[0, 1, 2, 3, 4, 5, 6]
[7, 8, 9, 10, 11, 12, 13]
[14, 15, 16, 17, 18, 19, 20]
[21, 22, 23, 24, 25, 26, 27]
[28, 29]

So with dates:

import itertools as it
start = DT.date(2008,5,5)
lenperiod = 14

for fnight,info in it.groupby(transactions,lambda data: (data[0]-start).days // lenperiod):
    print list(info)

You can use also weeknumbers from strftime, and lenperiod in number of weeks:

for fnight,info in it.groupby(transactions,lambda data: int (data[0].strftime('%W')) // lenperiod):
    print list(info)