If it says "strptime() argument 1 must be str, not Timestamp", likely that you already have the pandas.Timestamp object, i.e., it is not a string but a parsed date time, only it is in Pandas' format, not Python's. So to convert, use this:

date_time_obj = date.to_pydatetime()

instead of date_time_obj = datetime.strptime(date, '%Y-%m-%d %H:%M:%S')

I use ciso8601, which is 62x faster than datetime's strptime.

t = "01/12/2011"
ts = ciso8601.parse_datetime(t)
# to get time in seconds:
time.mktime(ts.timetuple())

You can learn more here.

This is for the text form of a timestamp that can be used in your text files. (The title of the question was different in the past, so the introduction to this answer was changed to clarify how it could be interpreted as the time. [updated 2016-01-14])

You can get the timestamp as a string using the .now() or .utcnow() of the datetime.datetime:

>>> import datetime
>>> print datetime.datetime.utcnow()
2012-12-15 10:14:51.898000

The now differs from utcnow as expected -- otherwise they work the same way:

>>> print datetime.datetime.now()
2012-12-15 11:15:09.205000

You can render the timestamp to the string explicitly:

>>> str(datetime.datetime.now())
'2012-12-15 11:15:24.984000'

Or you can be even more explicit to format the timestamp the way you like:

>>> datetime.datetime.now().strftime("%A, %d. %B %Y %I:%M%p")
'Saturday, 15. December 2012 11:19AM'

If you want the ISO format, use the .isoformat() method of the object:

>>> datetime.datetime.now().isoformat()
'2013-11-18T08:18:31.809000'

You can use these in variables for calculations and printing without conversions.

>>> ts = datetime.datetime.now()
>>> tf = datetime.datetime.now()
>>> te = tf - ts
>>> print ts
2015-04-21 12:02:19.209915
>>> print tf
2015-04-21 12:02:30.449895
>>> print te
0:00:11.239980