import re
import datetime
 
def is_date_valid(date_text):
	try:
		datetime.datetime.strptime(date_text, '%Y-%m-%d')
	except ValueError:
		return False
 
	return True
 
dane_z_pliku = """2007-01-12Jakis txt2008-01-31 xxx 2008-02-29 2008-15-10 2008-19-45 2009-05-01
20999-11-11 pppp 2001-00-01 09-01-01 2001-01-00 2009-01-111 2009-02-29 1998-11-11"""
 
regexp_result = re.findall("\d+-\d+-\d+", dane_z_pliku)
final_result = []
 
for date in regexp_result:
	if is_date_valid(date):
		final_result.append(date)
 
print (final_result)
 

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