No need to import time; datetime.datetime.strptime can do it by itself.

import datetime
dt=datetime.datetime.strptime(data[4]+data[5],'%Y%m%d%H%M%S')
print(dt)
# 2010-03-04 08:28:35

For information on the format codes (e.g. %Y%m%d%H%M%S) available, see the docs for strftime.

You're probably looking for formatGMT:

String output = DateTime.now().formatGMT('yyyyMMddHHmmss');
System.debug(output);

Note that MM is month, while mm is minute. This will give you the format you're looking for in GMT (GMT-00:00).

You can read SimpleDateFormat for all available options.

First part would be creating datetime object:

from datetime import datetime

date_string = "20190625091115"
format_date = datetime.strptime(date_string, '%Y%m%d%H%M%S'))
After which format date is:

print(format_date)
2019-06-25 09:11:15

Little clarification here, on python reference page, you can see definition for '%Y%m%d%H%M%S') format specifiers I used.

%Y: Year with century as a decimal number, e.g. 1970, 1988, 2001, 2013
%m: Month as a zero-padded decimal number (e.g. 01, 02, ..., 12)
%d: Day of the month as a zero-padded decimal number (e.g. 01, 02, ..., 31)
%H: Hour (24-hour clock) as a zero-padded decimal number (e.g 00, 01, ..., 23)
%M: Minute as a zero-padded decimal number (e.g 00, 01, ..., 59)
%S: Second as a zero-padded decimal number (e.g. 00, 01, ..., 59)
%f: Microsecond as a decimal number, zero-padded on the left (000000, 000001, ..., 999999)
%z: UTC offset in the form +HHMM or -HHMM, empty string if the the object is naive, (empty or +0000, -0400, +1030)

Use strftime:

>>> from datetime import datetime
>>> datetime.today().strftime('%Y-%m-%d')
'2021-01-26'

To also include a zero-padded Hour:Minute:Second at the end:

>>> datetime.today().strftime('%Y-%m-%d %H:%M:%S')
'2021-01-26 16:50:03'

To get the UTC date and time:

>>> datetime.utcnow().strftime('%Y-%m-%d %H:%M:%S')
'2021-01-27 00:50:03'