how to control formatting of a namedtuple in a list

[MRAB]

On 2016-11-17 23:49, Boylan, Ross wrote:
> Thank you; I can confirm that overriding __repr__ makes the list display as I wanted.
>
> The decision to use repr inside the list seems very odd, given the context, namely formatting something for display or looking for a simple string representation.  It seems more natural to me to use str or, if in a format, the default formatting all the way down.  Is there a good reason it's repr?
>
 > Ross

Given a string, say:

 >>> s = 'foo'

str shows:

 >>> print(str(s))

whereas repr shows:

 >>> print(repr(s))
'foo'

If it was in a list, would you want it to show:

[foo]

or:

['foo']

?

> ________________________________________
> From: Python-list [python-list-bounces+ross.boylan=ucsf.edu at python.org] on behalf of Chris Angelico [rosuav at gmail.com]
> Sent: Thursday, November 17, 2016 3:24 PM
> To: python-list at python.org
> Subject: Re: how to control formatting of a namedtuple in a list
>
> On Fri, Nov 18, 2016 at 10:04 AM, Boylan, Ross <Ross.Boylan at ucsf.edu> wrote:
>> Even after defining custom __str__ and __format__ methods they don't affect the display of objects when they are in a list.  Is there a way to change that, other than explicitly converting each list element to a string?
>>
>
> Yep! Inside a list, it's the repr that gets shown. So you should be
> able to do this:
>
> class Foo(namedtuple("Foo", "x")):
>     def __repr__(self):
>           return "foolish({})".format(self.x)
>
> This will also affect the other forms - if you don't define __str__,
> it'll use __repr__. So this should be all you need.
>
> ChrisA
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