A faster strptime?

Question

I have code which reads vast numbers of dates in 'YYYY-MM-DD' format. Parsing all these dates, so that it can add one, two, or three days then write back in the same format is slowing things down quite considerably.

 3214657   14.330    0.000  103.698    0.000 trade.py:56(effective)
 3218418   34.757    0.000   66.155    0.000 _strptime.py:295(_strptime)

 day = datetime.datetime.strptime(endofdaydate, "%Y-%m-%d").date()

Any suggestions how to speed it up a bit (or a lot)?

Answer 1

Is factor 7 lot enough?

datetime.datetime.strptime(a, '%Y-%m-%d').date()       # 8.87us

datetime.date(*map(int, a.split('-')))                 # 1.28us

EDIT: great idea with explicit slicing:

datetime.date(int(a[:4]), int(a[5:7]), int(a[8:10]))   # 1.06us

that makes factor 8.

Answer 2

For an ISO-formatted timezone-free string, eg.: "2021-01-04T14:30:03.123":

datetime.datetime(int(d[:4]), int(d[5:7]), int(d[8:10]), int(d[11:13]), int(d[14:16]), int(d[17:19]), int(d[20:]))

Seems to run faster than strptime() and fromisoformat().