Modifying the value of a float-like object

Dave Angel davea at
Thu Apr 16 02:55:37 CEST 2009

Steven D'Aprano wrote:
>>>> <snip>   
>>> Oh nonsense. Many programming languages have mutable floats.
>> That's irrelevant.  Python doesn't.  So introducing one will quite
>> likely alter the OP's code's behavior.  It doesn't matter if it's
>> possible, it matters whether the existing code's behavior might change,
>> and of course if a future maintainer might have trouble making sense of
>> it.
> What are you talking about? Python introduces new types quite frequently. 
> We now have sets, frozensets, rationals, decimals and namedtuples, and 
> we'll soon be getting ordereddicts and probably others as well. People 
> create new types in their code *all the time*, using the class statement. 
> If the OP wants to create a MutableFloat type, that's his prerogative.
The OP has existing code, and apparently a good deal of it, which he 
wants to run unchanged.  That's the whole purpose behind the 
discussion.  All I've been asserting is that  changing the variables 
that used to be floats to some new mutable-type would be risky to his 
code.  Since he's willing to assume the risk, then he can use the code 
which I proposed.  I'd much rather point out the risks, than have 
somebody paste something in and assume it'll work like before.

We'd better skip the discussion of other languages, since you're mixing 
terminology something awful.

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