Error handling in Python

[subhabrata . iisc]

Dear Members of the group,
If I open a url by urlopen in the urllib, the file is either opening a
file or if no url is there it would give error. The error is generated
can be handled by IOError handling schemes.
But if there are thousands or millions of URLs and I do not know who
will open and who won't open. How can I handle this kind of situation?
If any one can help solving this problem.
Regards,
Subhabrata.
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