Default __nonzero__ impl doesn't throw a TypeError exception

[Terry Reedy]

Sergey Kishchenko 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.

Sensible (and documented) defaults pervade Python.