[issue35174] Calling for super().__str__ seems to call self.__repr__ in list subclass

[Irit Katriel]

Change by Irit Katriel :


--
resolution:  -> not a bug
status: open -> closed

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[issue35174] Calling for super().__str__ seems to call self.__repr__ in list subclass

[Camion]

Camion  added the comment:

@Serhiy Storchaka, this doesn't seem logical, is certainly counter intuitive, 
and I fear there is a lack of expressivity.

- first of all, this is NOT about having str and repr returning the same at 
all, but about building the same _kind of_ structure representations for str 
and repr, but with str of sub elements in __str__, and with repr of sub 
elements in __repr__.

It is not logical at all and completely counter intuitive, if you explicitely 
ask str of the superclass, to get repr of the subclass. Getting repr of the 
superclass would be logical, but not repr of the subclass.

Now, it might happen that I missed another way to write what I tried (casting 
the object to it's super class with super(), to avoid explicitly naming the 
superclass) but if there is not, we then have something lacking in terms of 
expressivity.

--
resolution: not a bug -> 
status: closed -> open

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[issue35174] Calling for super().__str__ seems to call self.__repr__ in list subclass

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

list inherits __str__ from object. object.__str__() calls __repr__() which can 
be overridden in subclasses. So if you want repr() and str() returned the same, 
you need to define only the __repr__() method. This is a feature, not a bug.

--
nosy: +serhiy.storchaka
resolution:  -> not a bug
stage:  -> resolved
status: open -> closed

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[issue35174] Calling for super().__str__ seems to call self.__repr__ in list subclass

[Karthikeyan Singaravelan]

Karthikeyan Singaravelan  added the comment:

Adding the related StackOverflow question here for some context : 
https://stackoverflow.com/questions/53156623/calling-for-super-str-seem-to-call-self-repr-in-list-subclass

Thanks

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nosy: +xtreak

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[issue35174] Calling for super().__str__ seems to call self.__repr__ in list subclass

[Camion]

New submission from Camion :

I don't know if this is by design (for what reason ?) or if it is a bug, but I 
have noticed this quite counter-intuitive behaviour :

Doing that, it seems that the logical way to make the __repr__ and __str__ 
methods, would be to override respectively the parent __repr__ and _str__ 
methods, and calling them from the inherited versions, but for some reason, it 
seems that calling super().__str__ leads to call self.__repr__.

I have written the following piece of python-3 code in which I subclass the 
list class in order to make a class which supports storing names and unnamed 
fields the same way you can have variable named and unnamed parameters in a 
function call :

class struct(list):
def __init__(self, *args, **kwargs):
super().__init__(args)
for key, value in kwargs.items():
setattr(self, key, value)

def __repr__(self):
s = super().__repr__()[1:-1]
for key, val in self.__dict__.items():
s += ', '+key+'='+repr(val)
return 'struct('+s+')'

def __str__(self):
s = super().__str__()[1:-1]
print('Debug : super().__str__() = "'+super().__str__()+'"')
print('Debug : list(self).__str__() = "'+list(self).__str__()+'"')
print('Debug : s = "'+s+'"')
for key, val in self.__dict__.items():
s += ', '+key+'='+str(val)
return '{'+s+'}'

a = struct(1, 2, 3, a="akeja", b=21, c=True, d="lkj")
print('repr(a)="'+repr(a)+'"\n')
print('str(a)="'+str(a)+'"\n')

Executing this code in idle-3.5.2 will yield the following result :

>>> 
 RESTART: struct.py 
repr(a)="struct(1, 2, 3, b=21, d='lkj', a='akeja', c=True)"

Debug : super().__str__() = "struct(1, 2, 3, b=21, d='lkj', a='akeja', 
c=True)"
Debug : list(self).__str__() = "[1, 2, 3]"
Debug : s = "truct(1, 2, 3, b=21, d='lkj', a='akeja', c=True"
str(a)="{truct(1, 2, 3, b=21, d='lkj', a='akeja', c=True, b=21, d=lkj, 
a=akeja, c=True}"

>>> 

As one can see in the second debug lines, the call to `super().__str__()` which 
I expect to return the result from a call to the `__str__` function from my 
super class (`list`), will in fact return something which looks very much like 
the expected return from `self.__repr__()`

It seems that `super().__str__()` calls `self.__repr__()` instead of 
`list(self).__str__()` or even `super().__repr__()`.

--
components: Interpreter Core
messages: 329331
nosy: Camion
priority: normal
severity: normal
status: open
title: Calling for super().__str__ seems to call self.__repr__ in list subclass
type: behavior
versions: Python 3.5

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