All you need is in the documentation.

import time
time.strftime('%X %x %Z')
'16:08:12 05/08/03 AEST'

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

#python3

import datetime
print(
    '1: test-{date:%Y-%m-%d_%H:%M:%S}.txt'.format( date=datetime.datetime.now() )
    )

d = datetime.datetime.now()
print( "2a: {:%B %d, %Y}".format(d))

# see the f" to tell python this is a f string, no .format
print(f"2b: {d:%B %d, %Y}")

print(f"3: Today is {datetime.datetime.now():%Y-%m-%d} yay")

#4: to make the time timezone-aware pass timezone to .now()
tz = datetime.timezone.utc
ft = "%Y-%m-%dT%H:%M:%S%z"
t = datetime.datetime.now(tz=tz).strftime(ft)
print(f"4: timezone-aware time: {t}")

1: test-2018-02-14_16:40:52.txt

2a: March 04, 2018

2b: March 04, 2018

3: Today is 2018-11-11 yay

4: timezone-aware time: 2022-05-05T09:04:24+0000

Description:

Using the new string format to inject value into a string at placeholder {}, value is the current time.

Then rather than just displaying the raw value as {}, use formatting to obtain the correct date format.

https://docs.python.org/3/library/string.html#formatexamples

https://docs.python.org/3/library/datetime.html