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Groups > comp.lang.python > #15751

Re: suppressing import errors

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On 11/15/2011 4:20 PM, David Riley wrote:
...
>        None was set to some other value.  The other value might have a type
>        (such as a container) that could be false in a boolean context!
>
> Obviously, that last bit doesn't apply to modules; they're not going to evaluate as False in general.  I just bristle when I see people writing "if x" when they really mean "if x is not None", perhaps because it's not The Right Way(tm)?  It mostly comes down to aesthetics, I guess.  Write what you really mean.

Actually Dave, as your quote from PEP 8 says, the difference is real. 
It's not just aesthetics.

Consider this:

x = None
if x:
   print('if x == true')
else:
   print('if x == false')
if x is None:
   print('x is None == true')
else:
   print('x is none == false')

y = ''
if y:
   print('if y == true')
else:
   print('if y == false')
if y is None:
   print('y is None == true')
else:
   print('y is none == false')

The result is:

if x == false
x is None == true
if y == false
y is none == false

     Alan

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Re: suppressing import errors David Riley <fraveydank@gmail.com> - 2011-11-15 16:20 -0500
  Re: suppressing import errors Alan Meyer <ameyer2@yahoo.com> - 2011-11-15 17:59 -0500
    Re: suppressing import errors David Riley <fraveydank@gmail.com> - 2011-11-15 18:15 -0500

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