Serhiy Storchaka added the comment:
About length_hint():
I were mean something like (even explicit getattr() not needed):
try:
hint = type(obj).__length_hint__
except AttributeError:
return default
try:
val = hint(obj)
except TypeError:
return default
...
This is a little faster because there is only one attribute lookup instead two.
This is a little safer because there is a little less chance of race when an
attribute changed between two lookups (it is enough non-probably and doesn't
matter).
There is type(obj) here because the C code uses _PyObject_LookupSpecial() which
doesn't honor instance attributes and looks only class attributes.
About concat() and iconcat():
I think only first argument can be checked. If arguments are not concatenable
then '+'/'+=' operator will raise an exception. I'm not sure. Does anyone have
any thoughts about this?
About methodcaller():
Here is a catch. With this implementation you can't use `methodcaller('foo',
name='spam')` or `methodcaller('foo', self='spam')` (please add tests for those
cases). Here is a trick needed:
def __init__(*args, **kwargs):
self = args[0]
self._name = args[1]
self._args = args[2:]
self._kwargs = kwargs
(You can add a code for better error reporting).
I have added smaller comments on Rietveld.
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<http://bugs.python.org/issue16694>
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