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

[Dan Sommers]

On Wed, 06 Jul 2005 15:18:31 GMT,
Ron Adam <rrr at ronadam.com> wrote:

> 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 "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'

This is the one of which I was thinking.  So you see this error at the
end of a (long) traceback, and try to figure out where along the (long)
line of function calls I typed the wrong name.  Currently, the very end
of the traceback points you right at the bad code and says "NameError:
name 'filehandle' is not defined," which tells me (very nearly) exactly
what I did wrong.

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

s/u/a/

;-)

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

I guess it depends on how long your traceback is and how big those
functions are.  Also, from the Zen:

    Explicit is better than implicit.

although from previous threads, we know that every pythonista has his or
her own definitions of "explicit" and "implicit."

Regards,
Dan

-- 
Dan Sommers
<http://www.tombstonezero.net/dan/>