How to extract files with date pattern using python - regex

Question

I have n-files in a folder like
source_dir
abc_2017-07-01.tar
abc_2017-07-02.tar
abc_2017-07-03.tar
pqr_2017-07-02.tar
Lets consider for a single pattern now 'abc'
(but I get this pattern randomly from Database, so need double filtering,one for pattern and one for last day)
And I want to extract file of last day ie '2017-07-02'
Here I can get common files but not exact last_day files
Code
pattern = 'abc'
allfiles=os.listdir(source_dir)
m_files=[f for f in allfiles if str(f).startswith(pattern)]
print m_files
output:
[ 'abc_2017-07-01.tar' , 'abc_2017-07-02.tar' , 'abc_2017-07-03.tar' ]
This gives me all files related to abc pattern, but how can filter out only last day file of that pattern
Expected :
[ 'abc_2017-07-02.tar' ]
Thanks

Answer 1

just a minor tweak in your code can get you the desired result.
import os
from datetime import datetime, timedelta
allfiles=os.listdir(source_dir)
file_date = datetime.now() + timedelta(days=-1)
pattern = 'abc_' +str(file_date.date())
m_files=[f for f in allfiles if str(f).startswith(pattern)]
Hope this helps!

Answer 2

latest = max(m_files, key=lambda x: x[-14:-4])
will find the filename with latest date among filenames in m_files.

Answer 3

use python regex package like :
import re
import os
files = os.listdir(source_dir)
for file in files:
match = re.search('abc_2017-07-(\d{2})\.tar', file)
day = match.group(1)
and then you can work with day in the loop to do what ever you want. Like create that list:
import re
import os
def extract_day(name):
match = re.search('abc_2017-07-(\d{2})\.tar', file)
day = match.group(1)
return day
files = os.listdir(source_dir)
days = [extract_day(file) for file in files]
if the month is also variable you can substitute '07' with '\d\d' or also '\d{2}'. Be carefull if you have files that dont match with the pattern at all, then match.group() will cause an error since match is of type none. Then use :
def extract_day(name):
match = re.search('abc_2017-07-(\d{2})\.tar', file)
try:
day = match.group(1)
except :
day = None
return day