printing list, is this a bug?

[William Chang]

Is the different behavior between __repr__ and __str__ intentional
when it comes to printing lists? Basically I want to print out a list
with elements of my own class, but when I overwrite __str__, __str__
doesn't get called but if I overwrite __repr__, __repr__ will get
called. Is this a bug?



For example:
.... def __str__(self):
.... return "String Element"
....

a = [StrElement(), StrElement()]
print a

print StrElement()

String Element



But if overwrite __repr__:
.... def __repr__(self):
.... return "Repr Element"
....

b = [ReprElement(), ReprElement()]
print b

[Repr Element, Repr Element]
Repr Element

 

[Robert Kern]

Is the different behavior between __repr__ and __str__ intentional
when it comes to printing lists? Basically I want to print out a list
with elements of my own class, but when I overwrite __str__, __str__
doesn't get called but if I overwrite __repr__, __repr__ will get
called. Is this a bug?

No, it's deliberate design. The string representation of a list object, either
list.__str__() or list.__repr__(), uses the __repr__() of its contained objects.

--
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco

 

[William Chang]

oh okay. thanks.

 

[Dan Bishop]

Is the different behavior between __repr__ and __str__ intentional
when it comes to printing lists? Basically I want to print out a list
with elements of my own class, but when I overwrite __str__, __str__
doesn't get called but if I overwrite __repr__, __repr__ will get
called. Is this a bug?
...

As has been mentioned, this was a deliberate design decision. Partly
to make things like str(['a', 'b, c']) less confusing.