"import datetime" v.s. "from datetime import datetime"

Your trouble is that you have some code that is expecting datetime to be a reference to the datetime module and other code that is expecting datetime to be a reference to the datetime class. Obviously, it can't be both.

When you do:

from datetime import datetime
import datetime

You are first setting datetime to be a reference to the class, then immediately setting it to be a reference to the module. When you do it the other way around, it instead ends up being a reference to the class. Last assignment "wins."

You need to rename one of these references. For example:

import datetime as dt
from datetime import datetime

Then you can change references in the form datetime.xxxx that refer to the module to dt.xxxx.

Or else just import datetime and change all references to use the module name. In other words, if something just says datetime(...) you need to change that reference to datetime.datetime.

Python has a fair bit of this kind of thing in its library, unfortunately. If they followed their own naming guidelines in PEP 8, the datetime class would be named Datetime and there'd be no problem using both datetime to mean the module and Datetime to mean the class.

You cannot use both statements; the datetime module contains a datetime type. The local name datetime in your own module can only refer to one or the other.

Use only import datetime, then make sure that you always use datetime.datetime to refer to the contained type:

import datetime

today_date = datetime.date.today()
date_time = datetime.datetime.strptime(date_time_string, '%Y-%m-%d %H:%M')

Now datetime is the module, and you refer to the contained types via that.

Alternatively, import all types you need from the module:

from datetime import date, datetime

today_date = date.today()
date_time = datetime.strptime(date_time_string, '%Y-%m-%d %H:%M')

Here datetime is the type from the module. date is another type, from the same module.

datetime is a module which contains a type that is also called datetime. You appear to want to use both, but you're trying to use the same name to refer to both. The type and the module are two different things and you can't refer to both of them with the name datetime in your program.

If you need to use anything from the module besides the datetime type (as you apparently do), then you need to import the module with import datetime. You can then refer to the "date" type as datetime.date and the datetime type as datetime.datetime.

You could also do this:

from datetime import datetime, date
today_date = date.today()
date_time = datetime.strp(date_time_string, '%Y-%m-%d %H:%M')

Here you import only the names you need (the datetime and date types) and import them directly so you don't need to refer to the module itself at all.

Ultimately you have to decide what names from the module you need to use, and how best to use them. If you are only using one or two things from the module (e.g., just the date and datetime types), it may be okay to import those names directly. If you're using many things, it's probably better to import the module and access the things inside it using dot syntax, to avoid cluttering your global namespace with date-specific names.

Note also that, if you do import the module name itself, you can shorten the name to ease typing:

import datetime as dt
today_date = dt.date.today()
date_time = dt.datetime.strp(date_time_string, '%Y-%m-%d %H:%M')