pytz: conversion of POSIX timestamp to python timezone-aware datetime

ts_to_datetime.py

import pytz

def ts_to_datetime(ts, tz="UTC"):
    utc_dt = datetime.datetime.utcfromtimestamp(ts).replace(tzinfo=pytz.utc)
    tz = pytz.timezone(tz)
    dt = tz.normalize(utc_dt.astimezone(tz))
    return dt

# Reverse function is dt.timestamp()