python中datetime类型的utc时间如何转成时间戳？

Question

import datetime

now = datetime.datetime.utcnow()
这个now如何转成时间戳。。
用time.mktime(now.timetuple())这个方法产生的时间戳比time.time()产生的时间戳少28800秒，
现在我的方法是手动加上28800秒产生时间戳，，有没有更好的方法

Answer 1

import calendar
calendar.timegm(utc_timetuple)

Answer 2

Actually, the questioner here misunderstood the meaning of mktime. Let’s take a look at the official documentation of python:

time.mktime(t)
This is the inverse function of localtime(). Its argument is the struct_time or full 9-tuple (since the dst flag is needed; use -1 as the dst flag if it is unknown) which expresses the time in local time, not UTC. It returns a floating point number, for compatibility with time(). If the input value cannot be represented as a valid time, either OverflowError or ValueError will be raised (which depends on whether the invalid value is caught by Python or the underlying C libraries). The earliest date for which it can generate a time is platform-dependent.

mktime What is passed should be the local time, not the utc time, so if you want to get the timestamp of the specified utc time, the simpler method is:

1. Directly subtract the Unix timestamp start time, that is

timestamp = (now - datetime(1970, 1, 1)).total_seconds()

1. Convert to local time

now = datetime.datetime.now()
timestamp = time.mktime(now.timetuple())

Of course, there are many methods. Here are just two methods that are easier to understand. If you want to know more, here is a link for your reference: Converting datetime.date to UTC timestamp in Python

Answer 3

@yylucifer Well said. The main problem is timezone conversion.
For your problem, you can use the following method

# 基本上相等，但是会由于计算的耗时导致无法完全相等
# time.timezone：The offset of the local (non-DST) timezone, in seconds west of UTC 
time.mktime(datetime.datetime.utcnow().timetuple()) == time.time() + time.timezone