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convert given time from a given timezone to UTC

I have two inputs time 00:00 and timezone 'Asia/Kolkata'
I want to convert this to UTC time like '18.30'
I don't want to add or subtract offsets because it may affect the day light saving
what i did is
local = pytz.timezone ("UTC")
nativetime = datetime.strptime (setTime,frmt)
local_dt = local.localize(nativetime, is_dst=None)
utc_dt = local_dt.astimezone(pytz.utc)
but this doesn't change anything, the time is not converted to UTC
Please help

Something like this, assuming you're on py3:
>>> import datetime
>>> import pytz
>>> tz = pytz.timezone('Asia/Kolkata')
>>> dt = datetime.datetime(2020, 8, 4, 0, 0, tzinfo=tz)
>>> dt.astimezone(pytz.utc)
datetime.datetime(2020, 8, 3, 18, 7, tzinfo=<UTC>)
>>>

Since you say you're new to Python, it might be good to skip pytz since it's going to be deprecated with Python 3.9. You can use dateutil instead, which can be replaced more easily with zoneinfo in Python 3.9.
from datetime import datetime, timezone
from dateutil.tz import gettz
# assuming you have something like
dt_naive = datetime.strptime('2020-08-05', '%Y-%m-%d')
# dt_naive has no time zone info, so set it:
dt_aware = dt_naive.replace(tzinfo=gettz('Asia/Kolkata'))
# now you can convert to another timezone using .astimezone:
dt_aware_utc = dt_aware.astimezone(timezone.utc)
# datetime.datetime(2020, 8, 4, 18, 30, tzinfo=datetime.timezone.utc)
# -> 5:30 hours behind, which matches dt_aware.utcoffset()

#thebjorn gave me the answer
here is what i did
def utc_to_local(utc_dt,local_tz):
local_dt = utc_dt.replace(tzinfo=pytz.utc).astimezone(local_tz)
return local_tz.normalize(local_dt)
setTime='00:00:00'
setZone='Asia/Kolkata'
datePart = str(datetime.utcnow()).split(' ')[0]
dateTimeUtcStr = datePart+' '+str(setTime)
tz = pytz.timezone('Asia/Kolkata')
tz_utc = pytz.timezone('UTC')
dateTimeRef = datetime.strptime(dateTimeUtcStr, '%Y-%m-%d %H:%M:%S')
#local to utc
tzUtc = pytz.timezone('UTC')
local_dt = tz.localize(dateTimeRef, is_dst=None)
utc_dt = local_dt.astimezone(pytz.utc)
print(utc_dt)
#utc to local
altTime = utc_to_local(utc_dt,tz)
print(altTime)

Format a pattern string to display in desired format in Python

I do have a date and time format printed in '2020-05-06T15:16:24+05:30' which I would like to display in python in the format of YYYY-MMM-DD HH:MM:SS. Any pointers would be highly appreciated.

You have an ISO8601 datetime; yse the datetime module to parse a datetime object out of it, then format as required.
Note the timezone information is "hidden" in your desired formatting, but exists in that tzinfo property.
>>> s = '2020-05-06T15:16:24+05:30'
>>> import datetime
>>> t = datetime.datetime.fromisoformat(s)
datetime.datetime(2020, 5, 6, 15, 16, 24, tzinfo=datetime.timezone(datetime.timedelta(seconds=19800)))
>>> t.strftime("%Y-%m-%d %H:%M:%S")
'2020-05-06 15:16:24'
>>>

Python: Convert UTC time to localtime given UTC offset

Given the following Python datetime object representing an UTC time:
2016-09-15 22:13:03-2:00
I'm trying to obtain the corresponding local time datetime, where the UTC offset is applied:
2016-09-15 20:13:03
I was hoping to find a method in the datetime module that was able to do this, but I did not succeed. Any help is very appreciated.
Regards

I do not know if this is the best answer but here is what I have for you. Typically I would not do this since it is better to use the UTC time and convert
Here is a example:
value = datetime.datetime.strptime(str(utc_datetime), '%Y-%m-%d %H:%M:%S').replace(tzinfo=pytz.utc)
value = value.astimezone(pytz.timezone("America/Los_Angeles"))
I was unable to use your datetime as the syntax is a bit off so I went ahead and used dateutil.parser to convert it to a datetime object
>>> from dateutil.parser import parse
>>> val = parse('2016-09-15 22:13:03-2:00')
There are other ways to set a datetime object to UTC but I find pytz to be the easiest
>>> import pytz
>>> utc_val = val.replace(tzinfo=pytz.utc)
Here is the output of those two values. From here I grab the delta and subtract it
>>> val, utc_val
(datetime.datetime(2016, 9, 15, 22, 13, 3, tzinfo=tzoffset(None, -7200)), datetime.datetime(2016, 9, 15, 22, 13, 3, tzinfo=<UTC>))
>>>
>>> delta = val - utc_val
I remove the tzinfo since this is a converted datetime value
>>> local_dt = (val - delta).replace(tzinfo=None)
>>> local_dt
datetime.datetime(2016, 9, 15, 20, 13, 3)
>>> str(local_dt)
'2016-09-15 20:13:03'

How to get the difference in Localtime and GMT time python?

I get the server date and I need to get the difference of this date from GMT
I get
Datetime = "2011-04-27 2:17:45"
I would like to get the result like
Datetime = "2011-04-27 2:17:45 +0500"

Try this:
import datetime, pytz
now = datetime.datetime.now(pytz.timezone('Asia/Kolkata'))
print now.strftime('%Y-%m-%d %H:%M:%S %z')
# prints: '2011-04-27 13:56:09 +0530'

From the example you have given, it looks to me that what you are looking for is datetime.isoformat. The example in the page shows how to convert the datetime values to the ISO format with the time zone information.

To do this, you have to know the timezone (or the UTC offset) of the server date. What you have here is a "naive" date, without timezone info, you can't guess the UTC difference.

I think the datetime module is what you need here:
>>> from datetime import datetime
>>> datetime.now()
datetime.datetime(2011, 4, 27, 11, 8, 26, 149000)
>>> datetime.utcnow()
datetime.datetime(2011, 4, 27, 8, 8, 47, 712000)
For a difference between two dates:
>>> dtnow = datetime.now()
>>> dtutc = datetime.utcnow()
>>> dtnow - dtutc
datetime.timedelta(0, 10792, 847000)
Look up the datetime module and the relevant classes in Python's docs.

A very powerful extension of the datetime standard python library is the dateutil one, that allows you to easily:
set the delta of your time zone:
parse dates with various convenient options (in our case we will use the default option, which will allow us to set our time zone)
So 1st set time zone, and default date with this zone:
>>> from datetime import datetime
>>> from dateutil import parser
>>> from dateutil.tz import tzoffset
>>> tz_plus_5 = tzoffset(None, 5 * 60 * 60) # offset is in seconds !
>>> default = datetime.now(tz_plus_5)
Now use this default date in the parsing:
>>> Datetime = "2011-04-27 2:17:45"
>>> my_date = parser.parse(Datetime, default=default)
>>> my_date
datetime.datetime(2011, 4, 27, 2, 17, 45, tzinfo=tzoffset(None, 18000))
>>> my_date.strftime("%Y-%m-%d %H:%M:%S %z")
'2011-04-27 02:17:45 +0500'

For those that simply need to get the offset between local time and UTC, the time module has an attribute time.altzone that specifies the difference between UTC and local time in seconds:
The offset of the local DST timezone, in seconds west of UTC, if one is defined. This is negative if the local DST timezone is east of UTC (as in Western Europe, including the UK). Only use this if daylight is nonzero.
Here's an example of how it works:
>>> datetime.now().isoformat()
'2011-09-01T17:26:46.971000'
>>> datetime.utcnow().isoformat()
'2011-09-01T15:27:32.699000'
>>> time.altzone / (60*60)
-2
Doesn't get much cleaner than that.

Python Datetime : use strftime() with a timezone-aware date

Suppose I have date d like this :
>>> d
datetime(2009, 4, 19, 21, 12, tzinfo=tzoffset(None, -7200))
As you can see, it is "timezone aware", there is an offset of 2 Hour, utctime is
>>> d.utctimetuple()
time.struct_time(tm_year=2009, tm_mon=4, tm_mday=19,
tm_hour=23, tm_min=12, tm_sec=0,
tm_wday=6, tm_yday=109, tm_isdst=0)
So, real UTC date is 19th March 2009 23:12:00, right ?
Now I need to format my date in string, I use
>>> d.strftime('%Y-%m-%d %H:%M:%S.%f')
'2009-04-19 21:12:00.000000'
Which doesn't seems to take this offset into account. How to fix that ?

In addition to what #Slam has already answered:
If you want to output the UTC time without any offset, you can do
from datetime import timezone, datetime, timedelta
d = datetime(2009, 4, 19, 21, 12, tzinfo=timezone(timedelta(hours=-2)))
d.astimezone(timezone.utc).strftime('%Y-%m-%d %H:%M:%S.%f')
See datetime.astimezone in the Python docs.

The reason is python actually formatting your datetime object, not some "UTC at this point of time"
To show timezone in formatting, use %z or %Z.
Look for strf docs for details

This will convert your local time to UTC and print it:
import datetime, pytz
from dateutil.tz.tz import tzoffset
loc = datetime.datetime(2009, 4, 19, 21, 12, tzinfo=tzoffset(None, -7200))
print(loc.astimezone(pytz.utc).strftime('%Y-%m-%d %H:%M:%S.%f') )
(http://pytz.sourceforge.net/)

I couldn't import timezone module (and hadn't much time to know why)
so I set TZ environment variable which override the /etc/localtime information
>>> import os
>>> import datetime
>>> print datetime.datetime.now().strftime('%Y-%m-%d %H:%M')
2019-05-17 11:26
>>> os.environ["TZ"] = "UTC"
>>> print datetime.datetime.now().strftime('%Y-%m-%d %H:%M')
2019-05-17 09:26