检查日期时间对象中是否提供秒或微秒

Question

Is there a way to determine for a python datetime object if time attributes were included at the time the object was created? In particular, I would like to know if minutes, seconds or microseconds were provided.

For example, the following:

from datetime import datetime
d = datetime(2020,1,24)
# datetime.datetime(2020, 1, 24, 0, 0)
d.microsecond
# 0

# ideally, if function "has_seconds()" did exist...
if not d.has_seconds():
     d = d.replace(second=59)

I am working on a function where I receive a datetime object and I need to fill-in any information that was not provided originally. However, datetime assumes a value 0 for all time attributes that were not provided originally. Unfortunately, 0 is valid for hours, minutes, seconds and microseconds, so I cannot use that to check.

I am using Python 3.7, in case it's of relevance.

Answer 1

This isn't going to be possible with a datetime.datetime instance. As you note, the constructor automatically fills in missing values with 0 . Furthermore, there are other ways to create an instance of datetime.datetime beyond its constructor. There's no meaningful distinction between instances created by these various methods. If they have the same underlying value, they are equivalent and indistinguishable, by design. In other words, the datetime module is designed to actively discourage what you are trying to do.

Without knowing more about your specific use-case and why you need this behavior, it's difficult to suggest an alternative.

However, if you have control over the code that calls your function, your best bet is probably to define and accept your own datetime.datetime -like class that offers a similar constructor, but which does not implicitly replace unspecified values with 0 . Callers of your function would have to pass instances of your class instead of datetime.datetime . Once you have applied your custom "missing value" logic, you can create a fully-populated datetime.datetime object and proceed.