New submission from Andrew Lutomirski:
I'll admit that what I'm doing is possibly unhealthy. Nonetheless, I find this
behavior *extremely* surprising. This code:
--- start code ---
import datetime
class my_dt(datetime.datetime):
def __new__(cls, *args, **kwargs):
print('In my_dt.__new__')
return datetime.datetime.__new__(cls, *args, **kwargs)
def __init__(self, *args, **kwargs):
print('In my_dt.__init__')
super(my_dt, self).__init__()
dt = datetime.datetime.now()
print('Create a my_dt')
t = my_dt(dt.year, dt.month, dt.day, dt.hour, dt.minute, dt.second,
dt.microsecond, dt.tzinfo)
print('Calling replace')
t2 = t.replace(tzinfo=None)
print('Got a %r' % type(t2))
--- end code ---
results in:
Create a my_dt
In my_dt.__new__
In my_dt.__init__
Calling replace
Got a <class '__main__.my_dt'>
So datetime.datetime.replace will create an object of type my_dt *without
calling __new__ or __init__*. This should (AFAIK) be impossible.
I think that datetime.datetime.replace should either return an actual datetime
object or that it should invoke __new__ and probably __init__.
----------
components: Library (Lib)
messages: 208980
nosy: Andrew.Lutomirski
priority: normal
severity: normal
status: open
title: datetime.datetime.replace bypasses a subclass's __new__
versions: Python 3.3
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue20371>
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