On 8 янв, 22:03, "Chris Rebert" <c...@rebertia.com> wrote: > On Thu, Jan 8, 2009 at 5:53 AM, Sergey Kishchenko <void...@gmail.com> wrote: > > In Python empty container equals False in 'if' statements: > > > # prints "It's ok" > > if not []: > > print "It's ok" > > > Let's create a simple Foo class: > > > class Foo: > > pass > > > Now I can use Foo objects in 'if' statements: > > > #prints "Ouch!" > > f=Foo() > > if f: > > print "Ouch!" > > > So, default __nonzero__ impl is to return True. I think, this > > behaviour conflicts with 'Explicit is better than implicit' and > > 'Practicality beats purity' statements. I think, throwing a TypeError > > exception would be better. It will result in more explicit code with > > fewer errors. > > Python has a rich notion of boolean truth compared to other languages. > In this case, by default, non-None objects are considered True. It's a > reasonable default behavior since wanting to differentiate between > None and non-None objects is such a common task. > Also, I've been programming in Python for a long while and have yet to > encounter any bug due to this behavior. > Regarding the Zen, on the contrary, this is a perfect example of > "Practicality beats purity" in action. > > Cheers, > Chris > > -- > Follow the path of the Iguana...http://rebertia.com
I agree with you. I completely forget about differentiating between None and non-None objects. I think, thread can be closed. -- http://mail.python.org/mailman/listinfo/python-list
