Comments on: Is this pylint error message valid or bogus?

By: lindamoodbell

lindamoodbell — Tue, 30 Jun 2009 06:58:45 +0000

let me give this to my programmer this code, then i can let u know matt

By: Dave Kirby

Dave Kirby — Sat, 20 Jun 2009 14:37:38 +0000

I agree with the commenters on clp - as a user of the function looking at the signature, I would expect that initial_time needed to be a string.

If you wanted to use something more explicit than None, then you could use a placeholder object, e.g.

TODAY = object()
def midnight_next_day(initial_time=TODAY):
if initial_time is TODAY:
...

however pylint still complains that instance of object does not have a date method.

By: Ben Finney

Ben Finney — Sat, 20 Jun 2009 00:19:24 +0000

> The vast majority of pythoners use None, but I prefer descriptive strings for default values

If you do that, you're communicating badly.

Python's default arguments mean something very specific, and readers will expect it: “this argument can be omitted, and if so, *this value will be used instead*”. By putting a value there that you never intend on using, you subvert that communication.

Please, if you don't have a good static value to use, just stick with the conventional sentinel value: None.

If you need None for some other purpose (e.g. you need to tell the difference between the default and a user-supplied None), use a clearly-for-no-other-purpose object, such as a module-local name bound to a unique object() instance.

By: D'gou

D'gou — Fri, 19 Jun 2009 21:45:04 +0000

Nicely refactored.
“Gordian knot? What gordian knot? Just a bunch of pieces of rope on the floor here.”

By: Gary Bernhardt

Gary Bernhardt — Fri, 19 Jun 2009 20:45:16 +0000

I'd turn it into two functions: midnight_tomorrow() and midnight_after(initial_date). Default arguments tell you that you're probably violating the SRP. (Or maybe they're *always* violations; I haven't thought enough about it yet.) Here's a version with two functions:

def midnight_tomorrow():
....return midnight_after(datetime.now())

def midnight_after(initial_time):
....return initial_time.date() + timedelta(days=1)

There are no conditionals needed, it's two eloc instead of three, and there's less thinking required by the guy who calls these functions. The caller doesn't need the docstring suggested above by Alex or the descriptive default value you used; the functions' names are fully self-descriptive.

By: nes

nes — Fri, 19 Jun 2009 20:25:18 +0000

code does not come out that nice on the comment. Let's try this instead:

http://pastebin.com/m19049702

By: nes

nes — Fri, 19 Jun 2009 20:20:42 +0000

pylint thinks initial_time might be a string sometimes.

>>> def midnight_next_day(initial_time="use today's date"):

if initial_time == "use today's date":
initial_time = datetime.now()

return initial_time.date() + timedelta(days=1)

>>> midnight_next_day()

Traceback (most recent call last):
File "", line 1, in
midnight_next_day()
File "", line 6, in midnight_next_day
return initial_time.date() + timedelta(days=1)
AttributeError: 'str' object has no attribute 'date'
>>>

By: Alex

Alex — Fri, 19 Jun 2009 19:16:50 +0000

Sorry, but that's so nasty. Just use None and provide the description as a comment or in the docstring, please. None exists for a reason.

By: Anonymous

Anonymous — Fri, 19 Jun 2009 19:16:13 +0000

there is no need for an if statement:

initial_time = intial_time or datatime.now()

the original version is bad because it suggests that your functions is taking string parameters, where in fact it takes datetime objects. Misleading.