Python class with datetime.now() when instantiated

class, datetime, python

Solution

Default values for function parameters are computed once, when the function is defined. They are not re-evaluated when the function is called. Typically, you'd use `None` as the default value, and test for it in the body:

def __init__(self, created=None):
    self.created = created or datetime.now()

Even better, it looks like maybe you don't want to ever pass a created date into the constructor, in which case:

def __init__(self):
    self.created = datetime.now()

Problem

I want a Class attribute which sets `datetime.now()` when the a new instance of the class is instantiated. With this code, `MyThing.created` seems to always be when `MyThing` is imported, as opposed to when `mt` is instantiated. ``` from datetime import datetime class MyThing: __init__(self, created=datetime.now()): self.created = created MyThing.created datetime.datetime(2012, 7, 5, 10, 54, 24, 865791) mt = MyThing() mt.created datetime.datetime(2012, 7, 5, 10, 54, 24, 865791) ``` How can I do it so that `created` is when `mt` is instantiated, as opposed to `MyThing`?

Original source