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Re: Python : parsing the command line options using optparse

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  Re: Python : parsing the command line options using optparse Ganesh Pal <ganesh1pal@gmail.com> - 2014-03-01 16:43 +0530
    Re: Python : parsing the command line options using optparse Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-01 11:47 +0000
      Re: Python : parsing the command line options using optparse Ganesh Pal <ganesh1pal@gmail.com> - 2014-03-01 17:47 +0530

#67307 — Re: Python : parsing the command line options using optparse

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>
>
>
> Thanks  Peter  and Simon for the hints  it worked  : )  without ' ='
>
> # Python corrupt.py -o INODE -p /ifs/1.txt -q SET -f 1
>
> Current Default Choice :
>
> Choice: INODE
> Choice: SET
> Choice: 1
>
>
>
>

Iam done with the command line parsing but got stuck while trying to
implement switch kind of behavior with dictionaries.  So posting 2 more
questions



Question 1 :


Iam using the options.name  directly  for manipulations is this fine or do
I need to assign it to variable and then use it


Example:


Entered at cli #python corrupt.py -object_type INODE  --path_name/ifs/1.txt
-operation_type SET



Initialize all the command line option and then use it


object_type = options.object_type

path_name  = options.path_name

if object_type == 'LIN':

        corrupt_inode()

   elif  object_type  == 'DATA':

                corrupt_data()



               OR

if options.object_type == 'LIN':

       corrupt_inode()

   elif  options.object_type  == 'DATA':

         corrupt_data()

   elif  options.object_type  == 'INODE':

         corrupt_data()



#output

#python corrupt.py -object_type INODE  -p /ifs/1.txt -q SET -f 10

 -m 10  -n 123  -l  -c

Corrupted inode

_________________________________________________________________________________________________________


Question 2 :


I wanted to use dictionary to match the above if else behavior (we don't
have switch in python I guess ) and  If else looks very untidy.


Is it possible to store the options.object_type as a key in the dictionary
and   then based on the value entered in the command line invoke the
appropriate function



I tried creating a dictionary like this but Iam getting a wrong output




object_type_dictonary = { 'LIN' : corrupt_inode(),

                                      'INODE' : corrupt_lin(),

                                         'DATA' : corrupt_data(),

                   };


and then  ran # python corrupt.py -object_type= inode  (  This prints all
the values for me)


Example :

Corrupted inode

Corrupted LIN

Corrupted  data



PS : If user enters object_type= inode it should execute  corrupt_inode
  and print corrupted inode


Any help on  tips highly helpful :)

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#67310

On Sat, 01 Mar 2014 16:43:11 +0530, Ganesh Pal wrote:

> Iam done with the command line parsing but got stuck while trying to
> implement switch kind of behavior with dictionaries.  So posting 2 more
> questions

You should start new threads for new questions. The subject line here has 
nothing to do with the questions you ask.

> Question 1 :
> 
> Iam using the options.name  directly  for manipulations is this fine or
> do I need to assign it to variable and then use it

It is perfectly fine to use options.name directly. There's no need to 
save it to a temporary variable just to use it, unless doing this makes 
your code easier to read.


> Question 2 :
> 
> I wanted to use dictionary to match the above if else behavior (we don't
> have switch in python I guess ) and  If else looks very untidy.
> 
> Is it possible to store the options.object_type as a key in the
> dictionary and   then based on the value entered in the command line
> invoke the appropriate function

Yes. You almost got it right here:

> object_type_dictonary = { 'LIN' : corrupt_inode(),
>                           'INODE' : corrupt_lin(),
>                           'DATA' : corrupt_data(),
>                         };

(By the way, this is Python, not C, and there is no need for redundant 
semi-colons at the end of each line.)

The mistake you made is that you *called* the functions inside the dict. 
Instead, just refer to the function object itself, without calling it:

object_type_dictonary = {
    # no parens after the functions
    'LIN' : corrupt_inode,
    'INODE' : corrupt_lin,
    'DATA' : corrupt_data,
    }


Then, after you look up the object type, then and only then call the 
function:

func = object_type_dictionary[object_type]
func()



-- 
Steven

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#67313

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On Sat, Mar 1, 2014 at 5:17 PM, Steven D'Aprano <
steve+comp.lang.python@pearwood.info> wrote:

>
> You should start new threads for new questions. The subject line here has
> nothing to do with the questions you ask.
>
>

Sure Steven  and thanks for replying  and  your suggestion for Question 2
 ( same as  Peter Otten ) worked and Iam closing this thread now  :)

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