datetime.iterdate

[Robert Brewer]

Anyone else tired of typing date-addition logic when iterating? It would
be nice if the datetime package had something like:

def iterdates(first, last):
for day in range((last - first).days + 1):
yield first + datetime.timedelta(day)

....notice the inclusive boundaries (i.e. last gets returned). This
simple construct would make ugly date loops a lot cleaner:

for day in datetime.iterdates(first_date, last_date):
do_something_with(day)

Robert Brewer
MIS
Amor Ministries
fu******@amor.org

[Michele Simionato]

"Robert Brewer" <fu******@amor.org> wrote in message news:<ma*************************************@pyth on.org>...

Anyone else tired of typing date-addition logic when iterating? It would
be nice if the datetime package had something like:

def iterdates(first, last):
for day in range((last - first).days + 1):
yield first + datetime.timedelta(day)

...notice the inclusive boundaries (i.e. last gets returned). This
simple construct would make ugly date loops a lot cleaner:

for day in datetime.iterdates(first date, last date):
do something with(day)

Robert Brewer
MIS
Amor Ministries
fu******@amor.org

I actually asked the same four weeks ago (thread "datetime, calendar,
time intervals") since it is one of the first things I would have
expected to
find in the datetime module.

I don't see as a problem to add functions to modules (as opposed to
add new builtins which requires a lot of care). Is good to have even
simple functions in modules, if they are common, since you have the
advantage to have a stardard names for standard things, such as
interating
on time intervals. Of course, there should be the possibily of passing
a generic time step.
Michele Simionato

[Christopher T King]

On Sun, 11 Jul 2004, Robert Brewer wrote:

Anyone else tired of typing date-addition logic when iterating? It would
be nice if the datetime package had something like:

def iterdates(first, last):
for day in range((last - first).days + 1):
yield first + datetime.timedelta(day)

...notice the inclusive boundaries (i.e. last gets returned). This
simple construct would make ugly date loops a lot cleaner:

for day in datetime.iterdates(first_date, last_date):
do_something_with(day)

This is something that could be made simpler with a previous proposal I
had made to replace xrange():

for day in first_date<=datetime.days<=last_date:
do_something_with(day)

where datetime.days is an object representing the set of all days, and its
comparison functions return a subset of that set. To work perfectly, my
proposal needs only a slight change in the parser (to compile a<b<c as
(a<b)&(b<c) rather than a<b and b<c); I'm not sure how much this would
affect existing code though.

[Christos TZOTZIOY Georgiou]

On Mon, 12 Jul 2004 09:20:38 -0400, rumours say that Christopher T King
<sq******@WPI.EDU> might have written:

[snip of a<=x<=b proposition to replace xrange]

To work perfectly, my
proposal needs only a slight change in the parser (to compile a<b<c as
(a<b)&(b<c) rather than a<b and b<c); I'm not sure how much this would
affect existing code though.

A lot of code is based on "x and y" evaluating y only if x is true...
--
TZOTZIOY, I speak England very best,
"Tssss!" --Brad Pitt as Achilles in unprecedented Ancient Greek

[Christopher T King]

On Mon, 12 Jul 2004, Christos TZOTZIOY Georgiou wrote:

On Mon, 12 Jul 2004 09:20:38 -0400, rumours say that Christopher T King
<sq******@WPI.EDU> might have written:

[snip of a<=x<=b proposition to replace xrange]

To work perfectly, my
proposal needs only a slight change in the parser (to compile a<b<c as
(a<b)&(b<c) rather than a<b and b<c); I'm not sure how much this would
affect existing code though.

A lot of code is based on "x and y" evaluating y only if x is true...

Oh no, I don't mean to replace "x and y" with "x&y", I mean to replace the
expansion of "x<y<z" (which is currently "x<y and y<z") with
"(x<y)&(y<z)". This /would/ slightly change the semantics of the x<y<z
construct, but I pity the developer that relies on the short-circuitting
of the evaluation of 'z' if y<x is False (even though it is guaranteed by
the docs); any code that would be broken would have to look something like
this:

if do_A()==True==do_something_requiring_A_to_have_ret urned_True():
print 'Success!'

Nevertheless, perhaps a better expansion of x<y<z that would preserve
the original semantics would be:

e=x<y
if e:
e&=y<z
return e

[Larry Bates]

List comprehension to the rescue:

day_range=[first+datetime.timedelta(x) for x in range((last-first).days+1))]
for day in day_range:
do_something_with(day)

I'm not entirely sure the syntax is correct (I just
copied yours for the example) , but you get the idea.
I think it clearly defines the list of items you are
iterating over and keeps the definition close to the
loop where you do something (rather in a function
that may be defined far away in the code).

Larry Bates
Syscon, Inc.
"Robert Brewer" <fu******@amor.org> wrote in message
news:ma*************************************@pytho n.org...
Anyone else tired of typing date-addition logic when iterating? It would
be nice if the datetime package had something like:

def iterdates(first, last):
for day in range((last - first).days + 1):
yield first + datetime.timedelta(day)

....notice the inclusive boundaries (i.e. last gets returned). This
simple construct would make ugly date loops a lot cleaner:

for day in datetime.iterdates(first_date, last_date):
do_something_with(day)

Robert Brewer
MIS
Amor Ministries
fu******@amor.org