Python's datetime sucks June 28, 2014 on Drew DeVault's blog

I’ve been playing with Python for about a year now, and I like pretty much everything about it. There’s one thing that’s really rather bad and really should not be that bad, however - date & time support. It’s ridiculous how bad it is in Python. This is what you get with the standard datetime module:

What you don’t get is:

Date and time support is a rather tricky thing to do and it’s something that the standard library should support well enough to put it in the back of your mind instead of making you do all the work.

We’ll be comparing it to C# and .NET.

Let’s say I want to get the total hours between two datetimes.

// C#
DateTime a, b;
double hours = (b - a).TotalHours;
# Python
a, b = ...
hours = (b - a).seconds / 60 / 60

That’s not so bad. How about getting the time exactly one month in the future:

var a = DateTime.Now.AddMonths(1);
a = date.now() + timedelta(days=30)

Well, that’s not ideal. In C#, if you add one month to Janurary 30th, you get Feburary 28th (or leap day if appropriate). In Python, you could write a janky function to do this for you, or you could use the crappy alternative I wrote above.

How about if I want to take a delta between dates and show it somewhere, like a countdown? Say an event is happening at some point in the future and I want to print “3 days, 5 hours, 12 minutes, 10 seconds left”. This is distinct from the first example, which could give you “50 hours”, whereas this example would give you “2 days, 2 hours”.

DateTime future = ...;
var delta = future - DateTime.Now;
Console.WriteLine("{0} days, {1} hours, {2} minutes, {3} seconds left",
    delta.Days,
    delta.Hours,
    delta.Minutes,
    delta.Seconds);
# ...mess of math you have to implement yourself omitted...

Maybe I have a website where users can set their locale?

DateTime a = ...;
Console.WriteLine(a.ToString("some format string", user.Locale));
locale.setlocale(locale.LC_TIME, "sv_SE") # Global!
print(time.strftime("some format string"))

By the way, that Python one doesn’t work on Windows. It uses system locales names which are different on Windows than on Linux or OS X. Mono (cross-platform .NET) handles this for you on any system.

And a few other cases that are easy in .NET and not in Python:

In short, Python’s datetime module could really use a lot of fleshing out. This is common stuff and easy for a naive programmer to do wrong.

Have a comment on one of my posts? Start a discussion in my public inbox by sending an email to ~sircmpwn/public-inbox@lists.sr.ht [mailing list etiquette]

Articles from blogs I read Generated by openring

Site Redesign

Hey y’all! It’s been, gosh, what, ten years? I finally finished a total site redesign: all-new backend, HTML, CSS, modern image formats, etc. It’s finally readable on mobile now! There’s a lot of accumulated cruft in the database and filesystem–aphyr.com i…

via Aphyr: Posts March 28, 2021

What's cooking on SourceHut? March 2021

Hi! Another month of development has passed, and I’m here to fill you in on what’s new. Another 686 signups this month has brought us to 21,041 users. As always, I’ll be counting on you to make the new users feel at home, please be patient with them and help…

via Blogs on Sourcehut March 15, 2021

Status update, March 2021

Hi all! This month has been a little bit more quiet than others. I’ve spent a fair bit of time working on gamescope for Valve. As usual I’ve been fixing bugs and improving gamescope itself, but I’ve also worked on the rest of the ecosystem. I’m plumbing forma…

via emersion March 15, 2021