Aral Balkan

10 Oct 2008

Going from a datetime object to a string in Python:

import datetime
str(datetime.datetime.now())

>>> '2008-10-10 16:40:25.126049'

String to datetime: datetime.datetime.from_string('2008-10-10 16:40:25.126049')?

Nope, you need a bit more code courtesy of Kelly Yancey (or a C extension, which you cannot use on Google App Engine):

import re
from datetime import datetime
 
def parseDateTime(s):
	"""Create datetime object representing date/time
	   expressed in a string
 
	Takes a string in the format produced by calling str()
	on a python datetime object and returns a datetime
	instance that would produce that string.
 
	Acceptable formats are: "YYYY-MM-DD HH:MM:SS.ssssss+HH:MM",
							"YYYY-MM-DD HH:MM:SS.ssssss",
							"YYYY-MM-DD HH:MM:SS+HH:MM",
							"YYYY-MM-DD HH:MM:SS"
	Where ssssss represents fractional seconds.	 The timezone
	is optional and may be either positive or negative
	hours/minutes east of UTC.
	"""
	if s is None:
		return None
	# Split string in the form 2007-06-18 19:39:25.3300-07:00
	# into its constituent date/time, microseconds, and
	# timezone fields where microseconds and timezone are
	# optional.
	m = re.match(r'(.*?)(?:\.(\d+))?(([-+]\d{1,2}):(\d{2}))?$',
				 str(s))
	datestr, fractional, tzname, tzhour, tzmin = m.groups()
 
	# Create tzinfo object representing the timezone
	# expressed in the input string.  The names we give
	# for the timezones are lame: they are just the offset
	# from UTC (as it appeared in the input string).  We
	# handle UTC specially since it is a very common case
	# and we know its name.
	if tzname is None:
		tz = None
	else:
		tzhour, tzmin = int(tzhour), int(tzmin)
		if tzhour == tzmin == 0:
			tzname = 'UTC'
		tz = FixedOffset(timedelta(hours=tzhour,
								   minutes=tzmin), tzname)
 
	# Convert the date/time field into a python datetime
	# object.
	x = datetime.strptime(datestr, "%Y-%m-%d %H:%M:%S")
 
	# Convert the fractional second portion into a count
	# of microseconds.
	if fractional is None:
		fractional = '0'
	fracpower = 6 - len(fractional)
	fractional = float(fractional) * (10 ** fracpower)
 
	# Return updated datetime object with microseconds and
	# timezone information.
	return x.replace(microsecond=int(fractional), tzinfo=tz)

The datetime to string, easy; string to datetime… oh my, my! article by Aral Balkan, unless otherwise expressly stated, is licensed under a Creative Commons Attribution-Noncommercial 2.0 UK: England License.

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datetime to string, easy; string to datetime… oh my, my!

14 Comments »

Nice Regex! Makes the code so much shorter than doing it the long way.

John Dalziel
What about datetime.datetime.strptime(time_string, ‘%Y-%m-%d %H:%M:%S’)?
My date strings from client ignore sub-second but the format could be adjusted.

Bill
Could DateUtil be of help (as3 corelib, com.adobe.utils.DateUtil). For string to date conversion, they zhave parseRFC822, parseW3CDTF

A quick Actionscript 3 workaround for MS SQL Server default date-time parsing

When using Flex, the DateField control has a stringToDate method.

var dob:Date = DateField.stringToDate(”06/30/2005″, “MM/DD/YYYY”);

widged
thanks aral. l want to ask a question. oyur page rank 6 now. why. :(

htmlmekani
thank you admin

chat
it realy works. Thank you…

OzgurBatu
There’s a cheaper (as in “cheap-n-nasty”), more easily extensible method

The following code converts a timestamp or date string to a date object and prints it out (I needed to be able to do this for an arb reason):

#begin code
import datetime
import sys
import os

# much fudgery
def utctime(dt):
return (((dt.toordinal()-719163)*24+dt.hour)*60+dt.minute)*60+dt.second

def try_formats():
ret = []
ret.append(”%Y-%m-%d”)
ret.append(”%Y/%m/%d”)
ret.append(”%d/%m/%Y”)
ret.append(”%d-%m-%Y”)
ret.append(”%d/%m/%y”)
ret.append(”%d-%m-%y”)
ret.append(”%Y-%m-%d %H:%M:%S”)
ret.append(”%d-%m-%Y %H:%M:%S”)
ret.append(”%Y/%m/%d %H:%M:%S”)
ret.append(”%d/%m/%Y %H:%M:%S”)
ret.append(”%d-%m-%y %H:%M:%S”)
ret.append(”%y/%m/%d %H:%M:%S”)
ret.append(”%d/%m/%y %H:%M:%S”)
ret.append(”%Y-%m-%d %H:%M”)
ret.append(”%d-%m-%Y %H:%M”)
ret.append(”%Y/%m/%d %H:%M”)
ret.append(”%d/%m/%Y %H:%M”)
ret.append(”%d-%m-%y %H:%M”)
ret.append(”%y/%m/%d %H:%M”)
ret.append(”%d/%m/%y %H:%M”)
return ret

def show_date(s):
FORMAT=”%Y-%m-%d %H:%M:%S”
try:
secs = int(s)
d = datetime.datetime.fromtimestamp(secs)
print(str(secs) + ” :: ” + d.strftime(FORMAT))
return
except:
pass

for f in try_formats():
try:
d = datetime.datetime.strptime(s, f)
secs = utctime(d)
print(str(secs) + ” :: ” + d.strftime(FORMAT))
return
except:
pass

print(”Unable to grok datetime / int string ‘” + s + “‘”)

def usage():
print(os.path.basename(sys.argv[0]) + ” …”)
print(” attempts to grok the date from the string you provided and”)
print(” prints out a timestamp and date string for all arguments”)

if __name__ == “__main__”:
if len(sys.argv) == 1:
usage()
else:
for arg in sys.argv[1:]:
if (arg == “–help”) or (arg == “-h”):
usage()
else:
show_date(arg)

#end code

Hope it helps someone.

Dave
import datetime
import sys
import os

# much fudgery
def utctime(dt):
return (((dt.toordinal()-719163)*24+dt.hour)*60+dt.minute)*60+dt.second

def try_formats():
ret = []
ret.append(”%Y-%m-%d”)
ret.append(”%Y/%m/%d”)
ret.append(”%d/%m/%Y”)
ret.append(”%d-%m-%Y”)
ret.append(”%d/%m/%y”)
ret.append(”%d-%m-%y”)
ret.append(”%Y-%m-%d %H:%M:%S”)
ret.append(”%d-%m-%Y %H:%M:%S”)
ret.append(”%Y/%m/%d %H:%M:%S”)
ret.append(”%d/%m/%Y %H:%M:%S”)
ret.append(”%d-%m-%y %H:%M:%S”)
ret.append(”%y/%m/%d %H:%M:%S”)
ret.append(”%d/%m/%y %H:%M:%S”)
ret.append(”%Y-%m-%d %H:%M”)
ret.append(”%d-%m-%Y %H:%M”)
ret.append(”%Y/%m/%d %H:%M”)
ret.append(”%d/%m/%Y %H:%M”)
ret.append(”%d-%m-%y %H:%M”)
ret.append(”%y/%m/%d %H:%M”)
ret.append(”%d/%m/%y %H:%M”)
return ret

def show_date(s):
FORMAT=”%Y-%m-%d %H:%M:%S”
try:
secs = int(s)
d = datetime.datetime.fromtimestamp(secs)
print(str(secs) + ” :: ” + d.strftime(FORMAT))
return
except:
pass

for f in try_formats():
try:
d = datetime.datetime.strptime(s, f)
secs = utctime(d)
print(str(secs) + ” :: ” + d.strftime(FORMAT))
return
except:
pass

print(”Unable to grok datetime / int string ‘” + s + “‘”)

def usage():
print(os.path.basename(sys.argv[0]) + ” …”)
print(” attempts to grok the date from the string you provided and”)
print(” prints out a timestamp and date string for all arguments”)

if __name__ == “__main__”:
if len(sys.argv) == 1:
usage()
else:
for arg in sys.argv[1:]:
if (arg == “–help”) or (arg == “-h”):
usage()
else:
show_date(arg)

Dave
import datetime import sys import os
# much fudgery def utctime(dt): return (((dt.toordinal()-719163)*24+dt.hour)*60+dt.minute)*60+dt.second def try_formats(): ret = [] ret.append("%Y-%m-%d") ret.append("%Y/%m/%d") ret.append("%d/%m/%Y") ret.append("%d-%m-%Y") ret.append("%d/%m/%y") ret.append("%d-%m-%y") ret.append("%Y-%m-%d %H:%M:%S") ret.append("%d-%m-%Y %H:%M:%S") ret.append("%Y/%m/%d %H:%M:%S") ret.append("%d/%m/%Y %H:%M:%S") ret.append("%d-%m-%y %H:%M:%S") ret.append("%y/%m/%d %H:%M:%S") ret.append("%d/%m/%y %H:%M:%S") ret.append("%Y-%m-%d %H:%M") ret.append("%d-%m-%Y %H:%M") ret.append("%Y/%m/%d %H:%M") ret.append("%d/%m/%Y %H:%M") ret.append("%d-%m-%y %H:%M") ret.append("%y/%m/%d %H:%M") ret.append("%d/%m/%y %H:%M") return ret def show_date(s): FORMAT="%Y-%m-%d %H:%M:%S" try: secs = int(s) d = datetime.datetime.fromtimestamp(secs) print(str(secs) + " :: " + d.strftime(FORMAT)) return except: pass for f in try_formats(): try: d = datetime.datetime.strptime(s, f) secs = utctime(d) print(str(secs) + " :: " + d.strftime(FORMAT)) return except: pass print("Unable to grok datetime / int string '" + s + "'") def usage(): print(os.path.basename(sys.argv[0]) + " ...") print(" attempts to grok the date from the string you provided and") print(" prints out a timestamp and date string for all arguments")
if __name__ == "__main__": if len(sys.argv) == 1: usage() else: for arg in sys.argv[1:]: if (arg == "--help") or (arg == "-h"): usage() else: show_date(arg)

Dave
sorry, tried 3 times to post with indenting — as we all know, in python, whitespace counts!

If you can’t determine the proper indentation and you actually want the code, let me know by email:

davydm _AT_ gmail _DOT_ com

Sorry for the comment spam!

Dave
Thanks Man!
You saved me a lot of time

Thanks again

Shubhadeep
Datatype conversion heaven, this just made sense and worked.
I remember your skill from the Flash5 days and Flashkit, good to know you are still caring and sharing.

markvan
I came across this:
http://mail.python.org/pipermail/tutor/2006-March/045729.html

Code at this like has one error though, in last line instead of mytime it should be timestring

Himanshu
You can also use datetime.strptime(”date”,”format”) to convert string to datetime.

Note that the datetime.strptime returns a datetime object, if you want a datetime.date object you should call datetime.strptime(”date”,”format”).date().

I think it’s simpler.
Regards!

Caio

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