PLEAC-Python http://pleac.sourceforge.net/pleac_python/datesandtimes.html
- Dates and Times
Introduction
#----------------------------- #introduction # There are three common ways of manipulating dates in Python # mxDateTime - a popular third-party module (not discussed here) # time - a fairly low-level standard library module # datetime - a new library module for Python 2.3 and used for most of these samples # (I will use full names to show which module they are in, but you can also use # from datetime import datetime, timedelta and so on for convenience)
import time import datetime
print "Today is day", time.localtime()[7], "of the current year" # Today is day 218 of the current year
today = datetime.date.today() print "Today is day", today.timetuple()[7], "of ", today.year # Today is day 218 of 2003
print "Today is day", today.strftime("%j"), "of the current year" # Today is day 218 of the current year
Finding Today's Date
#----------------------------- # Finding todays date
today = datetime.date.today() print "The date is", today #=> The date is 2003-08-06
# the function strftime() (string-format time) produces nice formatting # All codes are detailed at http://www.python.org/doc/current/lib/module-time.html print t.strftime("four-digit year: %Y, two-digit year: %y, month: %m, day: %d") #=> four-digit year: 2003, two-digit year: 03, month: 08, day: 06
Converting DMYHMS to Epoch Seconds
#----------------------------- # Converting DMYHMS to Epoch Seconds # To work with Epoch Seconds, you need to use the time module
# For the local timezone t = datetime.datetime.now() print "Epoch Seconds:", time.mktime(t.timetuple()) #=> Epoch Seconds: 1060199000.0
# For UTC t = datetime.datetime.utcnow() print "Epoch Seconds:", time.mktime(t.timetuple()) #=> Epoch Seconds: 1060195503.0
Converting Epoch Seconds to DMYHMS
#----------------------------- # Converting Epoch Seconds to DMYHMS
now = datetime.datetime.fromtimestamp(EpochSeconds) #or use datetime.datetime.utcfromtimestamp() print now #=> datetime.datetime(2003, 8, 6, 20, 43, 20) print now.ctime() #=> Wed Aug 6 20:43:20 2003
# or with the time module oldtimetuple = time.localtime(EpochSeconds) # oldtimetuple contains (year, month, day, hour, minute, second, weekday, yearday, daylightSavingAdjustment) print oldtimetuple #=> (2003, 8, 6, 20, 43, 20, 2, 218, 1)
Adding to or Subtracting from a Date
#----------------------------- # Adding to or Subtracting from a Date # Use the rather nice datetime.timedelta objects
now = datetime.date(2003, 8, 6) difference1 = datetime.timedelta(days=1) difference2 = datetime.timedelta(weeks=-2)
print "One day in the future is:", now + difference1 #=> One day in the future is: 2003-08-07
print "Two weeks in the past is:", now + difference2 #=> Two weeks in the past is: 2003-07-23
print datetime.date(2003, 8, 6) - datetime.date(2000, 8, 6) #=> 1095 days, 0:00:00
#----------------------------- birthtime = datetime.datetime(1973, 01, 18, 3, 45, 50) # 1973-01-18 03:45:50
interval = datetime.timedelta(seconds=5, minutes=17, hours=2, days=55) then = birthtime + interval
print "Then is", then.ctime() #=> Then is Wed Mar 14 06:02:55 1973
print "Then is", then.strftime("%A %B %d %I:%M:%S %p %Y") #=> Then is Wednesday March 14 06:02:55 AM 1973
#----------------------------- when = datetime.datetime(1973, 1, 18) + datetime.timedelta(days=55) print "Nat was 55 days old on:", when.strftime("%m/%d/%Y").lstrip("0") #=> Nat was 55 days old on: 3/14/1973
Difference of Two Dates
#----------------------------- # Dates produce timedeltas when subtracted.
diff = date2 - date1 diff = datetime.date(year1, month1, day1) - datetime.date(year2, month2, day2) #-----------------------------
bree = datetime.datetime(1981, 6, 16, 4, 35, 25) nat = datetime.datetime(1973, 1, 18, 3, 45, 50)
difference = bree - nat print "There were", difference, "minutes between Nat and Bree" #=> There were 3071 days, 0:49:35 between Nat and Bree
weeks, days = divmod(difference.days, 7)
minutes, seconds = divmod(difference.seconds, 60) hours, minutes = divmod(minutes, 60)
print "%d weeks, %d days, %d:%d:%d" % (weeks, days, hours, minutes, seconds) #=> 438 weeks, 5 days, 0:49:35
#----------------------------- print "There were", difference.days, "days between Bree and Nat." #=> There were 3071 days between bree and nat
Day in a Week/Month/Year or Week Number
#----------------------------- # Day in a Week/Month/Year or Week Number
when = datetime.date(1981, 6, 16)
print "16/6/1981 was:" print when.strftime("Day %w of the week (a %A). Day %d of the month (%B).") print when.strftime("Day %j of the year (%Y), in week %W of the year.")
#=> 16/6/1981 was: #=> Day 2 of the week (a Tuesday). Day 16 of the month (June). #=> Day 167 of the year (1981), in week 24 of the year.
Parsing Dates and Times from Strings
#----------------------------- # Parsing Dates and Times from Strings
time.strptime("Tue Jun 16 20:18:03 1981") # (1981, 6, 16, 20, 18, 3, 1, 167, -1)
time.strptime("16/6/1981", "%d/%m/%Y") # (1981, 6, 16, 0, 0, 0, 1, 167, -1) # strptime() can use any of the formatting codes from time.strftime()
# The easiest way to convert this to a datetime seems to be; now = datetime.datetime(time.strptime("16/6/1981", "%d/%m/%Y")[0:5]) # the '' operator unpacks the tuple, producing the argument list.
Printing a Date
#----------------------------- # Printing a Date # Use datetime.strftime() - see helpfiles in distro or at python.org
print datetime.datetime.now().strftime("The date is %A (%a) %d/%m/%Y") #=> The date is Friday (Fri) 08/08/2003
High-Resolution Timers
#----------------------------- # High Resolution Timers
t1 = time.clock() # Do Stuff Here t2 = time.clock() print t2 - t1
# 2.27236813618 # Accuracy will depend on platform and OS, # but time.clock() uses the most accurate timer it can
time.clock(); time.clock() # 174485.51365466841 # 174485.55702610247
#----------------------------- # Also useful; import timeit code = '[x for x in range(10) if x % 2 == 0]' eval(code) # [0, 2, 4, 6, 8]
t = timeit.Timer(code) print "10,000 repeats of that code takes:", t.timeit(10000), "seconds" print "1,000,000 repeats of that code takes:", t.timeit(), "seconds"
# 10,000 repeats of that code takes: 0.128238644856 seconds # 1,000,000 repeats of that code takes: 12.5396490336 seconds
#----------------------------- import timeit code = 'import random; l = random.sample(xrange(10000000), 1000); l.sort()' t = timeit.Timer(code)
print "Create a list of a thousand random numbers. Sort the list. Repeated a thousand times." print "Average Time:", t.timeit(1000) / 1000 # Time taken: 5.24391507859
Short Sleeps
#----------------------------- # Short Sleeps
seconds = 3.1 time.sleep(seconds) print "boo"
Program: hopdelta
#----------------------------- # Program HopDelta # Save a raw email to disk and run "python hopdelta.py FILE" # and it will process the headers and show the time taken # for each server hop (nb: if server times are wrong, negative dates # might appear in the output).
import datetime, email, email.Utils import os, sys, time
- def extract_date(hop):
# According to RFC822, the date will be prefixed with # a semi-colon, and is the last part of a received # header. date_string = hop[hop.find(';')+2:] date_string = date_string.strip() time_tuple = email.Utils.parsedate(date_string)
# convert time_tuple to datetime EpochSeconds = time.mktime(time_tuple) dt = datetime.datetime.fromtimestamp(EpochSeconds) return dt
- def process(filename):
# Main email file processing # read the headers and process them f = file(filename, 'rb') msg = email.message_from_file(f)
hops = msg.get_all('received')
# in reverse order, get the server(s) and date/time involved hops.reverse() results = [] for hop in hops:
hop = hop.lower()
- if hop.startswith('by'): # 'Received: by' line
- sender = "start" receiver = hop[3:hop.find(' ',3)] date = extract_date(hop)
- else: # 'Received: from' line
- sender = hop[5:hop.find(' ',5)] by = hop.find('by ')+3 receiver = hop[by:hop.find(' ', by)] date = extract_date(hop)
results.append((sender, receiver, date))
output(results)
- def output(results):
print "Sender, Recipient, Time, Delta" print previous_dt = delta = 0 for (sender, receiver, date) in results:
- if previous_dt:
- delta = date - previous_dt
- print "%s, %s, %s, %s" % (sender,
- receiver, date.strftime("%Y/%d/%m %H:%M:%S"), delta)
print previous_dt = date
- def main():
# Perform some basic argument checking if len(sys.argv) != 2:
print "Usage: mailhop.py FILENAME"
- else:
filename = sys.argv[1] if os.path.isfile(filename):
process(filename)
- else:
- print filename, "doesn't seem to be a valid file."
- if __name__ == '__main__':
- main()