"""
@author Thomas Lehmann
@file dateBack.py
@brief provides a human readable format for a time delta
"""
from datetime import datetime , timedelta
def dateBack(theDateAndTime, precise=False, fromDate=None):
""" provides a human readable format for a time delta
@param theDateAndTime this is time equal or older than now or the date in 'fromDate'
@param precise when true then milliseconds and microseconds are included
@param fromDate when None the 'now' is used otherwise a concrete date is expected
@return the time delta as text
@note I don't calculate months and years because those varies (28,29,30 or 31 days a month
and 365 or 366 days the year depending on leap years). In addition please refer
to the documentation for timedelta limitations.
"""
if not fromDate:
fromDate = datetime.now()
if theDateAndTime > fromDate: return None
elif theDateAndTime == fromDate: return "now"
delta = fromDate - theDateAndTime
# the timedelta structure does not have all units; bigger units are converted
# into given smaller ones (hours -> seconds, minutes -> seconds, weeks > days, ...)
# but we need all units:
deltaMinutes = delta.seconds // 60
deltaHours = delta.seconds // 3600
deltaMinutes -= deltaHours * 60
deltaWeeks = delta.days // 7
deltaSeconds = delta.seconds - deltaMinutes * 60 - deltaHours * 3600
deltaDays = delta.days - deltaWeeks * 7
deltaMilliSeconds = delta.microseconds // 1000
deltaMicroSeconds = delta.microseconds - deltaMilliSeconds * 1000
valuesAndNames =[ (deltaWeeks ,"week" ), (deltaDays ,"day" ),
(deltaHours ,"hour" ), (deltaMinutes,"minute"),
(deltaSeconds,"second") ]
if precise:
valuesAndNames.append((deltaMilliSeconds, "millisecond"))
valuesAndNames.append((deltaMicroSeconds, "microsecond"))
text =""
for value, name in valuesAndNames:
if value > 0:
text += len(text) and ", " or ""
text += "%d %s" % (value, name)
text += (value > 1) and "s" or ""
# replacing last occurrence of a comma by an 'and'
if text.find(",") > 0:
text = " and ".join(text.rsplit(", ",1))
return text
def test():
""" testing function "dateBack" """
# we need a date to rely on for testing concrete deltas
fromDate = datetime(year=2012, month=4, day=26, hour=8, minute=40, second=45)
testCases = [
("1 second" , fromDate-timedelta(seconds=1), False),
("5 seconds" , fromDate-timedelta(seconds=5), False),
("1 minute" , fromDate-timedelta(minutes=1), False),
("5 minutes" , fromDate-timedelta(minutes=5), False),
("1 minute and 10 seconds" , fromDate-timedelta(minutes=1, seconds=10), False),
("1 hour" , fromDate-timedelta(hours= 1), False),
("1 hour and 1 second" , fromDate-timedelta(hours=1, seconds=1), False),
("1 hour and 1 minute" , fromDate-timedelta(hours=1, minutes=1), False),
("1 hour, 1 minute and 1 second" , fromDate-timedelta(hours=1, minutes=1, seconds=1), False),
("1 week" , fromDate-timedelta(weeks=1), False),
("2 weeks" , fromDate-timedelta(weeks=2), False),
("1 week and 1 second" , fromDate-timedelta(weeks=1, seconds=1), False),
("1 week and 1 minute" , fromDate-timedelta(weeks=1, minutes=1), False),
("1 week and 1 hour" , fromDate-timedelta(weeks=1, hours=1), False),
("1 week, 1 hour, 1 minute and 1 second", fromDate-timedelta(weeks=1, hours=1, minutes=1, seconds=1), False),
("1 millisecond" , fromDate-timedelta(milliseconds=1),True),
("2 milliseconds" , fromDate-timedelta(milliseconds=2),True),
("1 microsecond" , fromDate-timedelta(microseconds=1),True),
("2 microseconds" , fromDate-timedelta(microseconds=2),True),
("1 millisecond and 1 microsecond" , fromDate-timedelta(milliseconds=1, microseconds=1),True) ]
for expectedResult, testDate, precise in testCases:
print("test case for '%s'" % expectedResult)
calculatedResult = dateBack(testDate, precise=precise, fromDate=fromDate)
try: assert expectedResult == calculatedResult
except: print(" -> error: wrong value: '%s'" % calculatedResult)
# future date in relation to 'fromDate' (1 hour)
futureDate = fromDate + timedelta(hours=1)
expectedResult = None
assert expectedResult == dateBack(futureDate, precise=False, fromDate=fromDate)
if __name__ == "__main__":
test()
