sub-classing the types in the builtin module datetime

Michael Amrhein mamrhein at
Wed Aug 15 19:03:20 CEST 2007

Colin J. Williams wrote:
> I wish to sub-class (if that's the right word) datetime and to use a 
> different signature for the constructor.
> The second part has gone smoothly, but it is difficult to access the 
> type's methods from the sub-class instance.
What's difficult?
 >>> from datetime import datetime
 >>> class mydt(datetime): pass
 >>> dt=mydt(2007,8,15)
mydt(2007, 8, 15, 18, 57, 58, 562000)

How did you overwrite the constuctor?
Are you sure your constructor really returns a subclass of datetime?

> I'm beginning to wonder whether it might might be simpler to write my 
> own Date class.
If you only want to change the signature of the constuctor, just write a 
factory function.

> Does anyone have any comments please?
> Colin W.

Have fun,

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