[Python-ideas] %-formatting with Decimals

[Ethan Furman]

On 03/11/2014 02:51 PM, random832 at fastmail.us wrote:
> On Tue, Mar 11, 2014, at 16:25, Ethan Furman wrote:
>> at some point prior, random832 at fastmail.us wrote:
>>>
>>> Is % formatting not going to be updated to support new features
>>
>> No.
>>
>>> or fix bugs like this?
>>
>> It's not a bug.  Decimal is not float.
>
> The bug to which I was referring involves not calling __format__ on
> whatever object is passed in as str.format does - Decimal not being
> float is no impediment to str.format and Decimal.__format__ accepting
> the same format strings that float.__format__ does.

That is not a bug.  str.__mod__ is not documented as calling an object's __format__ method, and indeed it does not.


>>>   Is it going to be deprecated?
>>
>> No.  %-formatting has its place.
>
> What place is that?
>
>      There should be one-- and preferably only one --obvious way to do
>      it.

You'll notice the word 'preferably' in there.  The preferred method is format.  %-formatting has a good place in lazy 
evaluation (in logging, for example), as well as other areas.


> We've got two syntaxes, and two functions, that do _almost_ the same
> thing, but with two completely different microlanguages. Why?

Because % was there first, but had some failings that are addressed by format.

--
~Ethan~