How to check if a datetime object is localized with pytz?

Question

I want to store a datetime object with a localized UTC timezone. The method that stores the datetime object can be given a non-localized datetime (naive) object or an object that already has been localized. How do I determine if localization is needed?

Code with missing if condition:

class MyClass:
  def set_date(self, d):
    # what do i check here?
    # if(d.tzinfo):
      self.date = d.astimezone(pytz.utc)
    # else:
      self.date = pytz.utc.localize(d)

Answer 1

How do I determine if localization is needed?

From datetime docs:

• a datetime object d is aware iff:

  d.tzinfo is not None and d.tzinfo.utcoffset(d) is not None
  

• d is naive iff:

  d.tzinfo is None or d.tzinfo.utcoffset(d) is None
  

Though if d is a datetime object representing time in UTC timezone then you could use in both cases:

self.date = d.replace(tzinfo=pytz.utc)

It works regardless d is timezone-aware or naive.

Note: don't use datetime.replace() method with a timezone with a non-fixed utc offset (it is ok to use it with UTC timezone but otherwise you should use tz.localize() method).