Re: 'if name is not None:' v. 'if name:'

[Victor Noagbodji]

>>what's the difference between these two statement?

>one checks if the given object is not None, the other checks if it's a true value:
http://docs.python.org/ref/Booleans.html#Booleans

>>And which one should one use?

depends on what you want to test for, of course.

</F>

Well that's exactly why I'm asking. Since None returns False in if
statements. Why do people use if name is not None: instead of simply
writing if not name?

--
NOAGBODJI Paul Victor

[Jeffrey Froman]

Victor Noagbodji wrote:

Why do people use if name is not None: instead of simply
writing if not name?

To differentiate from the case where name == '', or some other non-None
false value. So the question is, do you want to test for identity with
None, or for truth in general?
Jeffrey

[Matimus]

On Jul 15, 12:44*pm, "Victor Noagbodji" <[e-mail]>
wrote:

>what's the difference between these two statement?

one checks if the given object is not None, the other checks if it's a true value:
http://docs.python.org/ref/Booleans.html#Booleans

>And which one should one use?

depends on what you want to test for, of course.

</F>

Well that's exactly why I'm asking. Since None returns False in if
statements. Why do people use if name is not None: instead of simply
writing if not name?

--
NOAGBODJI Paul Victor

1. If you want to distinguish between None and something else that
evaluates to False.
2. Speed, "is not" is checking identity of the objects. That can be
(and usually is) much quicker than checking whether or not it
evaluates to True. Checking the boolean value calls the "__nonzero__"
method of an object. That method could be user defined and very
complex.

In general there are many cases where you use "None" as a placeholder
(similar to NULL in C/C++). The best practice is to always compare
identity with None.

Matt