[Python-ideas] FormatRepr in reprlib for declaring simple repr functions easily

[Ronny Pfannschmidt]

Hi,

i consider my utility class FormatRepr finished,
its currently availiable in
( http://pypi.python.org/pypi/reprtools/0.1 )

it supplies a descriptor that allows to simply declare __repr__ methods
based on object attributes.

i think it greatly enhances readability for those things,
as its DRY and focuses on the parts *i* consider important
(e.E. what accessible attribute gets formatted how)

there is no need ot repeat attribute names or
care if something is a property,class-attribute or object attribute
(one of the reasons why a simple .format(**vars(self)) will not always work)

oversimplified example:


.. code-block:: python

from reprtools import FormatRepr

class User(object):
__repr__ = FormatRepr("<User {name}>")

def __init__(self, name):
self.name = name



>>> User('test')
<User test>



-- Ronny
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[Mike Graham]

On Wed, May 30, 2012 at 11:03 AM, Ronny Pfannschmidt
<Ronny.Pfa...@gmx.de> wrote:
> Hi,
>
> i consider my utility class FormatRepr finished,
> its currently availiable in
> ( http://pypi.python.org/pypi/reprtools/0.1 )
>
> it supplies a descriptor that allows to simply declare __repr__ methods
> based on object attributes.
>
> i think it greatly enhances readability for those things,
> as its DRY and focuses on the parts *i* consider important
> (e.E. what accessible attribute gets formatted how)
>
> there is no need ot repeat attribute names or
> care if something is a property,class-attribute or object attribute
> (one of the reasons why a simple .format(**vars(self)) will not always work)
>
> oversimplified example:
>
>
> .. code-block:: python
>
>   from reprtools import FormatRepr
>
>   class User(object):
>       __repr__ = FormatRepr("<User {name}>")
>
>       def __init__(self, name):
>           self.name = name
>
>
>
>>>> User('test')
> <User test>

If we introduce something like this, I think I'd prefer an approach
that didn't encourage hardcoding "User". In my __repr__s, I usually
make the class's name dynamic so it does not make for confusing reprs
in the event of subclassing.

You really don't end up implementing __repr__ all that often and if
you do you writing a simple one isn't hard. I'm -0 on having this in
the stdlib.

Mike

[Ronny Pfannschmidt]

you can just use {__class__.__name__} to have it "softcoded"

[Alexandre Zani]

I would prefer an interface where I just pass a list of attribute
names and the utility class figures everything else out.

That said, I'm not sure this does enough to warrant inclusion in the
stdlib. It's easy enough to write a __repr__ with just a few more
characters. I'm not sure that:

__repr__ = FormatRepr("<User {username}>"

is actually more readable than

def __repr__(self):
return "<User %s>" % self.username

In fact, the second option might be better because I don't have to
learn anything new to understand it. If I see your version, I have to
google it and then use brain-space to hold that feature in memory. If
I know python, I already know what the second option means.

Alexandre Zani

On Thu, May 31, 2012 at 7:43 AM, Ronny Pfannschmidt