[Python-Dev] dateutil (original) (raw)

Gustavo Niemeyer niemeyer at conectiva.com
Mon Mar 15 09:14:17 EST 2004

> d.forwardmonths(3).endofmonth()

In dateutil, I think it's d + relativedelta(months=+1, day=1, days=-1). Arguably, this is fairly trivial (highly non-obvious, but trivial...)

Yes, it'd work, but "d + relativedelta(day=31)" would be enough.

It's a trade-off, power at the cost of comprehensibility. I've always been a fan of flexible, powerful tools (and I'm sure the readability of my code suffers for it :-)). So I prefer relativedelta.

Thanks! I belive it'd also be easy to implement the interface mentioned by Greg on top of relativedelta.

Some use cases that I find hard with "bare" datetime (all are real requirements for me):

1. For a date d, get the start and end of the month containing it. (many "report this month" jobs)

(just as examples)

d + relativedelta(day=1) d + relativedelta(day=31)

2. For a date d, get the start and end of the month before it. (equivalent "report last month" jobs). This is just (1) plus the need to subtract "roughly" a month from a date.

d + relativedelta(months=-1, day=1) d + relativedelta(months=-1, day=31)

3. 12 noon on the first Thursday of next month. (Don't blame me, that's when we have a maintenance slot on one of our systems).

d + relativedelta(months=+1, day=1, weekday=TH, hour=12)

4. The last Friday of the month. (End-of-month reporting time).

d + relativedelta(day=31, weekday=FR(-1))

The key functionality here is "add N months" and "go to weekday N (forward or backward)". Both things that the core datetime avoids for well-explained reasons.

Agreed.

I'm happy with dateutil as it stands, outside of the core. If it's to go into the core, I agree that a PEP would be the right thing to do. And probably not just one - separate PEPS for the different areas would focus discussion better: [...]

Understood. Thanks for your comments.

-- Gustavo Niemeyer http://niemeyer.net

More information about the Python-Dev mailing list