python - 为什么 datetime.now(datetime.timezone.utc) 和 datetime.datetime.utcnow() 之间存在差异

Question

如果您调用 datetime.datetime.now(datetime.timezone.utc) 您会得到类似 datetime.datetime(2021, 9, 8, 1, 33, 19, 684253, tzinfo=datetime.timezone.utc).

如果您调用 datetime.datetime.utcnow()，您会得到类似 datetime.datetime(2021, 9, 8, 1, 33, 20, 283212) .

结果看似相同，但实际上并非如此，因为时间戳会有所不同。例如。调用 datetime.datetime.now(datetime.timezone.utc).timestamp() - datetime.datetime.utcnow().timestamp() 返回(对我来说):-18000.000012159348.

这是为什么？

import datetime

print()
print(datetime.datetime.now(datetime.timezone.utc))
print(datetime.datetime.utcnow())

print()
print(datetime.datetime.now(datetime.timezone.utc).timestamp())
print(datetime.datetime.utcnow().timestamp())
print(datetime.datetime.now(datetime.timezone.utc).timestamp() - datetime.datetime.utcnow().timestamp())

Answer 1

此行为已记录。发生这种情况是因为 utcnow() 返回一个简单的日期时间。

datetime.utcnow()

Return the current UTC date and time, with tzinfo None.

This is like now(), but returns the current UTC date and time, as anaive datetime object. An aware current UTC datetime can be obtainedby calling datetime.now(timezone.utc).

这就是为什么文档还提到了 datetime.now()

This function is preferred over today() and utcnow().