Before getting to your specific question, a few remarks below:
On 28Mar2019 12:08, Matthew Herzog <matthew.her...@gmail.com> wrote:
I have cobbled together this code which gives me regex matches of files
whose names either begin with either YYYYMMDD_? or erased_YYMMDD_? and
whose extensions are exml or ewav.
todaystring = date.today().strftime("%Y%m%d")
oldest = date.today() - timedelta(days=180)
def get_files(extensions):
all_files = []
for ext in extensions:
all_files.extend(Path('/Users/msh/Python/calls').glob(ext))
return all_files
for file in get_files(('*.ewav', '*.exml')):
print(re.match("[0-9]{8}|erased_",file.name))
Your regexp in the "print" loop at the bottom does not do what you say.
You have:
print(re.match("[0-9]{8}|erased_",file.name))
i.e. the regexp is:
[0-9]{8}|erased_
(a) That matches 8 digits _or_ the string "erased_".
(b) [0-9] can be written as \d for more readability.
(c) I'd use:
(erased_)?\d{8}
which is an optional "erased_" followed by 8 digits. And for your
purposes:
(erased_)?(\d{8})
which will group the digits together for easy extraction:
DATED_FILENAME_re = re.compile(r'(erased_)?(\d{8})')
for file in get_files(('*.ewav', '*.exml')):
m = DATED_FILENAME_re.match(file)
if m:
# a suitable filename
datepart = m.group(2)
# now you can turn that into an actual datetime.date object
Now I need to compare the date string (regex match) in the filename to
today's date. If the result of the comparison results in YYYMMDD being
older than 180 days, I should print something to indicate this. If not,
nothing need be done.
Should I write another function to compare each matched regex to today's
date or is that overkill? Thanks.
If you want to figure out the age, you need to convert the YYYYMMDD into
a datetime.date and then compare _that_ to today's date. Why? Because
the datetime.date type knows how to work with dates correctly, avoiding
all sorts of bug prone efforts on your own part (because human calendars
are irregular tricky things with many special cases).
So I would drop the "todaystring" altogether. You're thinking "get the
string from the filename and compare it to "todaystring". But what you
_want_ it to measure the age, and that requires working with dates, not
strings. So instead convert the filename's string in to a date and do
straight arithmetic with today().
So you might upgrade that regexp to group the year, month and day
individually, pull them out and make a date object:
import datetime
........
DATED_FILENAME_re = re.compile(r'(erased_)?(\d\d\d\d)(\d\d)(\d\d)')
........
# get today as a datetime.date object
today = datetime.today()
for file in ......:
m = DATED_FILENAME_re.match(file)
if m:
prefix, year, month, day = m.group(1,2,3,4)
year = int(year)
month = int(month)
day = int(day)
# turn this into a datetime.date object
date = datetime.date(year, month, day)
# compute a datetime.timedelta object
age = today - date
if age.days > 180:
print("old!")
I think you're right: make a function to return the datetime.date of the
filename, so this portion:
m = DATED_FILENAME_re.match(file)
if m:
prefix, year, month, day = m.group(1,2,3,4)
year = int(year)
month = int(month)
day = int(day)
# turn this into a datetime.date object
date = datetime.date(year, month, day)
and return the computed date. Then just keep this in the for loop so it
is obvious what's going on; it is too small to hide in a function
without a better reason.
# compute a datetime.timedelta object
age = today - date
if age.days > 180:
print("old!")
Cheers,
Cameron Simpson <c...@cskk.id.au>
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