Hello,
One of the first lessons in the tutorial is to define a __unicode__ method. In
Python 3, __unicode__ is replaced by __str__ (and __str__ by __bytes__, but
that method won't be needed in general).
Writing these methods in a way works on both Python 2 and 3 proves surprisingly
messy. I'd like some feedback before choosing a technique, applying it to
Django, and documenting it.
Here are a few proposals. Which one do you prefer? Do you have better ideas?
* Proposal 1 — the very explicit way
+ explicit
+ no runtime overhead
- not DRY
- much boilerplate code
from __future__ import unicode_literals
from django.utils import six
class MyClass(object):
if six.PY3:
def __str__(self):
return "text ..."
else:
def __str__(self):
return self.__unicode__().encode('utf-8')
def __unicode__(self):
return "text ..."
* Proposal 2 — the Python 3 way
+ explicit
+ no runtime overhead
- 3 lines of boilerplate code
from __future__ import unicode_literals
from django.utils import six
class MyClass(object):
def __str__(self):
return "text ..."
if not six.PY3:
__unicode__ = __str__
__str__ = lambda self: self.__unicode__().encode('utf-8')
* Proposal 3 — the magic mixin
+ no boilerplate code
- not explicit
- requires writing a __unicode__ method which was removed in Python 3: this
is non-educational for Python 2 programmers learning Python 3 and complete
nonsense for Python 3 programmers who have never been exposed to Python 2.
from __future__ import unicode_literals
from django.utils.encoding import StrAndUnicode
class MyClass(StrAndUnicode, object):
def __unicode__(self):
return "text ..."
* Proposal 4 — the non-unicode way
- on Python 2, __unicode__ performs an unnecessary encode / decode
- on Python 2, __unicode__ will fail if the system encoding isn't utf-8
(which may happen for a variety of reasons)
from __future__ import unicode_literals
from django.utils import six
class MyClass(object):
def __str__(self):
result = "text ..."
if six.PY3:
result = result.encode('utf-8')
return result
At this point I tend to prefer the version 2, because it's explicit, short and
in line with our goal to write Python 3 code that also works on Python 2. What
about you?
Best regards,
--
Aymeric.
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