function to check whether a variable already exists?

[Roman Suzi]

On Tue, 1 May 2001, Graham Guttocks wrote:

>Can anyone tell me how to wrap the following in a function as to
>avoid typing this try, except sequence for every variable whose
>existence I want to check?
>
>For example,
>
>try:
>    if NEWSRC:pass
>except NameError:
>    NEWSRC = os.path.expanduser("~/.newsrc")

try: NEWSRC
except: NEWSRC = ...

or:

if not vars().has_key("NEWSRC"): NEWSRC = ...

or:

myvars = [('NEWSRC', """os.path.expanduser("...")"""),
           ...
  ]

for (v, default) in myvars:
  try: eval(v)
  except: exec v + " = " + default


-- really bad solution, speaking of bad design.

It will be interesting to hear others.

>It seems tricky, because you can't just pass a function NEWSRC because
>if it doesn't first exist NameError will immediately be raised.
>
>Regards,
>Graham
>
>__________________________________________________
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>
>

Sincerely yours, Roman Suzi
-- 
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