CODEWITHSUNDEEP
pythonparameters
user2909312
user2909312

Reputation: 65

how to set optional input parameter in python

I have the following snippet where i am checking for first argument and runninginto following error..can anyone help on how to make the first argument optional?

SNIPPET CODE:-

branch = ''
if  sys.argv[1]:
    branch = sys.argv[1]

ERROR:-

Traceback (most recent call last):
  File "test.py", line 102, in <module>
    main()
  File "test.py", line 66, in main
    if  sys.argv[1]:
IndexError: list index out of range

Upvotes: 1

Views: 958

Answers (3)

RMcG
RMcG

Reputation: 1095

For inputting parameters into python you can use the getopt module. Here parameters can be optional and can be inputted in any order as long at the correct flag is present.

In the example below the user has two optional parameters to set, the input-file name and the database name. The code can be called using

python example.py -f test.txt -d HelloWorld

or

python example.py file=test.txt database=HelloWorld

or a mix and match of both. The flags and names can be changed to reflect your needs.

import getopt

def main(argv):
     inputFileName = ''
     databaseName = ''
     try:                                                                     
         opts, args = getopt.getopt(argv,"f:d:",["file=","database="])
     except getopt.GetoptError:                                                
         print('-f <inputfile> -d <databasename> -c  <collectionname>')
         sys.exit()
     for opt, arg in opts:                                                     
         if opt in ('-f','--file'):                                              
             inputFileName = arg                                                
         elif opt in ('-d','--database'):                                        
             databaseName = arg

if __name__ == "__main__":
    main(sys.argv[1:])

Upvotes: 1

Konstantin Kovrizhnykh
Konstantin Kovrizhnykh

Reputation: 191

You can use:

branch = sys.argv[1] if len(sys.argv) >= 2 else ''

Upvotes: 0

Ashwini Chaudhary
Ashwini Chaudhary

Reputation: 250951

Use exception handling(EAFP):

try:
    branch = sys.argv[1]
except IndexError:
    branch = ''

Upvotes: 0

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