>>> from datetime import datetime
>>> datetime.now().year
2017
>>> def my():
...     year = 3017
...     print('hello mymy')
...
>>> my().year
hello mymy
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'year'
>>>

 >>> def my():
...     year = 3017
...     print('hello mymy')

 AttributeError: 'NoneType' object has no attribute 'year'

 class MyDate:
    def __init__(self, day, month, year):
        self.day = day
        self.month = month
        self.year = year
def my():
    year = 3017
    date_instance = MyDate(1, 1, year)
    return date_instance
my().year # будет 3017