map/filter/reduce/lambda opinions and background unscientific mini-survey

[Ron Adam]

Dan Sommers wrote:

> On Wed, 06 Jul 2005 14:33:47 GMT,
> Ron Adam <rrr at ronadam.com> wrote:
> 
> 
>>Since this is a Python 3k item...  What would be the consequence of
>>making None the default value of an undefined name?  And then assigning
>>a name to None as a way to delete it?
> 
> 
> [ ... ]
> 
> 
>>Any drawbacks?
> 
> 
> Lots more hard-to-find errors from code like this:
> 
>     filehandle = open( 'somefile' )
>     do_something_with_an_open_file( file_handle )
>     filehandle.close( )
> 
> Regards,
> Dan


If do_something_with_an_open_file() is not defined. Then you will get:

     TypeError: 'NoneType' object is not callable


If "file_handle" (vs "filehandle") is None.  Then you will still get an 
error as soon as you tried to use the invalid file handle.

     AttributeError: 'NoneType' object has no attribute 'read'


If the error was filehundle.close()  you will get:

     AttributeError: 'NoneType' object has no attribute 'close'


I don't think any of those would be hard to find.


Cheers,
Ron