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Python and SQL timezones

I'm using python to create a datetime value with Europe/London timezone:
import datetime
from pytz import timezone, utc
now_utc = datetime.datetime.now()
now_uk = now_utc.astimezone(timezone('Europe/London')) # convert to local time
I then want to add this value to a SQL database using sqlite3 within python.
cursor = con.cursor()
sql_data = ("INSERT INTO TCADATA (datetime, gym1) VALUES (datetime(:datetime), :gym1;")
cursor.execute(sql_data, {"datetime":now_uk, "gym1":data["gym1"]})
The value that gets added to the SQL database is one hour different from my London timezone, so if it's 16:00 here, the value in the database is 15:00.
My guess is that SQLite3 is converting the datetime to UTC.
How do I specify to sqlite that the value is a London time zone? I would prefer to specify London like I have done with python, rather than GMT since this changes at daylight savings.
Or perhaps it would be simpler to keep it as UTC and convert it to London time when the data is read?

I think the best way to get round this issue is to either store the datetimes in UTC timezone on the server and convert to local time zones as needed when retrieving the data in python.

Timestamp to non UTC Datetime object is substracting hours twice

I have the following timestamp 1550588656 which translates to 2019-02-19 15:04:16+00:00 in UTC time convention.
I want to convert it to my country's time convention (UTC or GMT -3 in this time of the year) so it should translate to 2019-02-19 12:04:16+00:00
I have read on other SO questions that first I have to convert the timestamp to an UTC aware Datetime object and then localize it, I'm doing it like this
# string format time
naive_datetime = datetime.fromtimestamp(timestamp).strftime('%Y-%m-%d %H:%M:%S')
# string parse time
naive_datetime = datetime.strptime(naive_datetime, "%Y-%m-%d %H:%M:%S")
# make naive Datetime object UTC aware
utc_datetime = naive_datetime.replace(tzinfo=pytz.UTC)
So now it's not a naive Datetime object, from here I should be able to localize it to my country's timezone. In Python that is pytz.timezone('America/Santiago')
So it should go something like this
cltime = pytz.timezone('America/Santiago')
local_datetime = utc_datetime.astimezone(cltime)
But I'm getting 2019-02-19 09:04:16-03:00 (UTC or GTM -6 ) as a result and I don't know why.
Can someone explain? My intuition tells me it's probably a simple thing I'm not looking at, but I've spent some minutes in it and I haven't been able to tell yet.

If you look at the documentation for fromtimestamp:
Return the local date and time corresponding to the POSIX timestamp
So the problem is that it is already doing a conversion from UTC to the local time, and you're doing it a second time.

First of all you have epoc time (UTC timestamp). You need to convert it into datetime object (native) which is followed by converting native time to aware time and than finally convert it to your local time.
Convert your timestamp to native datetime object
native_datetime = datetime.fromtimestamp(1550588656)
convert native datetime object to aware time (add timezone info, will add timezone info to native timezone UTC for current)
import pytz
utc_time = native_datetime.replace(tzinfo=pytz.timezone("UTC"))
localising aware datetime to your local datetime
local_time = utc_time.astimezone(pytz.timezone("America/Santiago"))
You can replace "America/Santiago" with your local time zone
I think this would help you to solve your problem. Thanks!

Convert timestamp to postgres timestamp

Currently i have the following timestamp format as below :
2018-04-02T09:00:00+09:30
How can i convert the timestamp above to suit the postgres's timestamp column like below?
2018-04-02 09:00:00 +09.30
Also how can use python to convert the xml timestamp first before loading into postgres table?

This doesn't require any conversion whatsoever, it's a regular ISO 8601 time stamp. PostgreSQL supports multiple input formats for time stamps
select timestamp with time zone '2018-04-02T09:00:00+09:30';
timestamptz
------------------------
2018-04-01 18:30:00-05
(1 row)
You'll notice it's storing it in UTC. That's what you want. From the docs,
For timestamp with time zone, the internally stored value is always in UTC (Universal Coordinated Time, traditionally known as Greenwich Mean Time, GMT). An input value that has an explicit time zone specified is converted to UTC using the appropriate offset for that time zone. If no time zone is stated in the input string, then it is assumed to be in the time zone indicated by the system's TimeZone parameter, and is converted to UTC using the offset for the timezone zone.
When a timestamp with time zone value is output, it is always converted from UTC to the current timezone zone, and displayed as local time in that zone. To see the time in another time zone, either change timezone or use the AT TIME ZONE construct (see Section 9.9.3).

If you know you will always get your data in that format, you can do something like:
>>> a = "2018-04-02T09:00:00+09:30"
>>>
>>> b = a.replace('T', ' ').replace('+', ' +')
>>> b
'2018-04-02 09:00:00 +09:30'
It is ugly, but it works.
It is always safer to interpret your input as a date and then print it in the desired format.

I am Not able to convert the unix time to local date and time in PYTHON

I wanted to convert the UNIX time into local date and time. I am getting the UNIX timestamp value from my server but when I convert the UNIX using these set of code I get a time which is 1 hour 30 min less than the actual time. But when I take the raw timestamp data and check in the online UNIX to local date and time converter I get the correct time.
import datetime
time_local = datetime.datetime.fromtimestamp(1502705627085/1e3)
print time_local

is your timezone correct on your system ?
From the python datetime documentation :
classmethod datetime.fromtimestamp(timestamp[, tz])
Return the local date and time corresponding to the POSIX timestamp, such as is returned by time.time(). If optional argument tz is None or not specified, the timestamp is converted to the platform’s local date and time, and the returned datetime object is naive.
If you cannot change your system's timezone, you can specify a tz as explained in the datetime module documentation.

import datetime
import tzlocal
time_local = datetime.datetime.fromtimestamp(1502705627085/1e3, tzlocal.get_localzone())
print time_local

How to get time from PostgreSQL in the same TZ, which was initialy used while uploading to DB, instead of UTC?

There are datetimes that are uploaded to DB by Django in the format “2015-10-31 17:00:00+03” (aware form of time).
PostgreSQL keeps time in UTC
In pgAdmin I see my datetimes as “2015-10-31 17:00:00+03” instead of UTC.
Is it possible to get from DB “2015-10-31 17:00:00+03” instead of “2015-10-31 14:00:00+00”? As I understand, if datetime is aware, there is TZ info in the value in DB, but how to take this TZ?
For example, I want to upload a new datetimes, but before to write to DB, I want to compare these datetimes with the values ​​that already exist in the database. So, a new part of datetimes have format:
“2015-10-31 17:00:00+03”, but the values ​​are taken from the database is UTC, ie
“2015-10-31 14:00:00+00”, when it should be also 17:00:00+03!
How to get value from DB not in UTC, but in TZ +3 (for this example)?
test = Shows.objects.get(name = 'Test')
test.date_time # I get UTC, but I need to get it as TZ +3
PS: hardcoding like this
from pytz import timezone
right_time = utc_from_db.astimezone(timezone('Europe/Berlin'))
is impossible. It is necessary to get exactly the time zone from the database that was originally filled with a value, because all datetimes ​​may have different time zone.

As I was informed, seems it is impossible. PostgreSQL uses TZ from awared type of time to convert time to UTC and can't be converted back natively.
If I want to get back UTC-ed time from DB to the time with TZ it was initially, I can make one more column in DB and put there the name of TZ, such as 'Europe/Berlin' and convert time from DB with UTC to initial time with proper TZ like this (the same code as in the question part):
from pytz import timezone
right_time = utc_from_db.astimezone(timezone('Europe/Berlin'))