[Tutor] Two Questions...(i) Checking for None (ii) Making command line arguments mutually exclusive

[Asrarahmed Kadri]

Hi Folks,

I am trying to build a program which takes the following command-line
arguments:

   *-s <IP address> -D <start date> -n <no. of days> -t <start time>  <end
time>*

the first argument which is -s (for source) can be replaced by -d (for
destination) or -o (for observer) or -r (for reporter). Now what I want is
to make sure that the user only supplies one of the options from the 4
alternatives.

I am using 'optparse' module. It has got a nice feature taht enables you to
give the option name, along with the variable-name to store the value of
that option. The syntax is as under:


from optparse import OptionParser
parser = OptionParser()                    # make an object of OptionParser
parser.add_option("-s", action="store", type="string", dest="source_ip" )  #
mapping argument to the value and storing it in souce_ip

My second question is about chekcing for None type. The issue is that
optionParser sets the value = None for all the options that are not
specified by the user. So suppose if the user doesnt specify -t, then time
would be set to None. How to check the None type.

TIA.
Regards,
Asrarahmed

-- 
To HIM you shall return.
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