Coerce with new style classes

Alex Martelli aleax at
Mon Feb 24 09:33:49 CET 2003

Blair Hall wrote:

> I can't seem to use coerce with the new style classes,
> any suggestions?

Coercion is going away, though it may be hard to find solid information
about what's going away from where when.

See PEP 208, for more.

In particular, you can find some current details at:


It is no longer recommended to define a coercion operation. Mixed-mode 
operations on types that don't define coercion pass the original arguments 
to the operation. 

New-style classes (those derived from object) never invoke the __coerce__() 
method in response to a binary operator; the only time __coerce__() is 
invoked is when the built-in function coerce() is called. 

and you're apparently being bitten by the second of these
two points I'm quoting.


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