How to know when a variable is set

Justin Dubs jtdubs at eos.ncsu.edu
Wed Nov 14 16:34:11 CET 2001


"-" <madsurfer2000 at hotmail.com> wrote in message
news:fef0a228.0111140715.24b5cfc7 at posting.google.com...
> How can I test if a variable has been given a value, or if it's undefined?

I'm a bit of a newbie, but offhand:

>>> dir()
['__builtins__', '__doc__', '__name__']
>>> foo = 5
>>> dir()
['__builtins__', '__doc__', '__name__', 'foo']
>>> 'foo' in dir()
1
>>> 'bar' in dir()
0
>>> if 'foo' in dir():
...     print "foo exists"
... else:
...     print "foo doesn't exist"
...
foo exists
>>> print ["foo doesn't exist", "foo exists"]['foo' in dir()]
foo exists
>>> print ["bar doesn't exist", "bar exists"]['bar' in dir()]
bar doesn't exist
>>> bar = 0
>>> print ["bar doesn't exist", "bar exists"]['bar' in dir()]
bar exists

Hehe.  That was kinda fun.  Well, you get the idea.  There may be a much
better way, but, like I said, I'm really new to Python.  I liked that one
though.  :-).  Have a good day,

Justin Dubs





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