Boolean tests

[Ethan Furman]

Matthew Woodcraft wrote:
> Ben Finney  <bignose+hates-spam at benfinney.id.au> wrote:
> 
>>No, he retracted the *insult* and restated the *advice* as a distinct
>>statement. I think it's quite worthwhile to help people see the
>>difference.
> 
> 
> Ben, it was quite clear from Anders' post that he knows about
> __nonzero__ . That's why the so-called advice is insulting. The
> original phrasing was just the icing on the cake.
> 
> -M-

I got just the opposite -- it seems quite clear to me that Anders did 
*not* know about __nonzero__, and perhaps doesn't know about 
double-underscore functions in general...

Here's his quote:

 > Okay, so you have this interesting object property that you often need
 > to test for, so you wrap the code for the test up in a method, because
 > that way you only need to write the complex formula once.  I'm with
 > you so far.  But then you decide to name the method "__nonzero__",
 > instead of some nice descriptive name?  What's up with that?

His last question, "What's up with that?" is the indicator.  His 
comments after that, such as

 > Even if we find out that C.__nonzero__ is called, what was it that
 > __nonzero__ did again?

reinforce the impression that he is unaware of the double-underscore 
functions and what they do and how they work.  One can find out when 
they are called with a simple search of the python documentation.

 > Better dig up the class C documentation and find out, because there is
 > no single obvious interpretation of what is means for an object to
 > evaluate to true.

If you are using somebody else's code, and maybe even your own, you 
should always check the docs if you don't know/can't remember what a 
function does.
~Ethan~