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if: elif: else:...

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if: elif: else:... Python Programming forum discussing coding techniques, tips and tricks, and Zope related information. Python was designed from the ground up to be a completely object-oriented programming language.

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  #1  
Old May 16th, 2003, 12:38 PM
bulliver bulliver is offline
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if: elif: else:...
Hello all...


Having problems with a script. Heres the relevant section:
Code:
if sys.argv[1] == '-dir':
	convertDirectory(sys.argv[2])

elif sys.argv[1] == '--help':
    showUsage()

elif string.count(sys.argv[1], '.mp3') == 1:
    convertSong(sys.argv[1])

else:
    showUsage()

What I want is if no command line arguments are given, the usage details are shown. When I test it with no arguments however, I get an error telling me that sys.argv[1] is out of range, which is true: it doesn't exist, which is kinda the point.

The traceback shows the error as:
'Traceback (most recent call last):
File "./dir2ogg.py", line 82, in ?
if sys.argv[1] == '-dir':
IndexError: list index out of range'

I tried testing for sys.argv[1] ie: elif sys.argv[1] == 0: but always get the out of range error.

What am I doing wrong here? It seems as though python is ignoring my catchall else: clause. When the other clauses are tested they work as they should.
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  #2  
Old May 17th, 2003, 08:58 AM
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telex4 telex4 is offline
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Try this (I can't test it at the mo, so it's off the top of my head)

PHP Code:
if not sys.argv[1]:
    showUsage()

elif if sys.argv[1] is '-dir':
    convertDirectory(sys.argv[2])

elif sys.argv[1] is '--help':
    showUsage()

elif string.count(sys.argv[1], '.mp3') is 1:
    convertSong(sys.argv[1]) 


You might also want to look at the module getopt, which is pretty handy in cases like this.
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  #3  
Old May 17th, 2003, 02:25 PM
bulliver bulliver is offline
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Thanks for the reply. It didn't work, but it got me thinking. I reordered the if, else's and tested for the length of sys.argv
here's the code:
Code:
if len(sys.argv) < 2:
    showUsage()

elif sys.argv[1] == '-dir':
        convertDirectory(sys.argv[2])

elif sys.argv[1] == '--help':
    showUsage()

elif string.count(sys.argv[1], '.mp3') == 1:
    convertSong(sys.argv[1])

else:
    showUsage()


Works perfect now...

thanks for the help
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  #4  
Old May 22nd, 2003, 09:35 AM
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Jcaputo Jcaputo is offline
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Bulliver, did you get this to work?
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  #5  
Old May 22nd, 2003, 02:08 PM
bulliver bulliver is offline
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Yes I did

that last bit of code I posted did the trick...
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  #6  
Old May 22nd, 2003, 02:24 PM
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Excellent - thanks for the update!
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