Peter Otten wrote:
> Mel wrote:
>> Grant Edwards wrote:
>>> On 2009-09-22, Brown, Rodrick <rodrick.br...@citi.com> wrote:
>>>
>>>> How could I do the following check in Python
>>>>
>>>> In Perl I could do something like if ((defined($a)) { ... }
>>>
[ ... ]
> This is an artifact of the interactive interpreter,
True. You can avoid the artifact by wrapping the test in a function:
Python 2.6.2 (release26-maint, Apr 19 2009, 01:56:41)
[GCC 4.3.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> class A():
... def __repr__ (self):
... return b
...
>>> def is_defined (obj):
... try:
... obj
... except NameError:
... return False
... return True
...
>>> a = A()
>>> if is_defined (a):
... print "`a` is defined"
... else:
... print "`a` is not defined"
...
`a` is defined
>>> if is_defined (b):
... print "`b` is defined"
... else:
... print "`b` is not defined"
...
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'b' is not defined
>>>
At the cost of it not quite working when the function is called with an
undefined name. I suppose the print statements could be crafted to make it
look better.
Mel.
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