How do I add an optional flag to my command line args?
eg. so I can write
python myprog.py
or
python myprog.py -w
I tried
parser.add_argument('-w')
But I just get an error message saying
Usage [-w W]
error: argument -w: expected one argument
which I take it means that it wants an argument value for the -w option. What's the way of just accepting a flag?
I'm finding http://docs.python.org/library/argparse.html rather opaque on this question.
As you have it, the argument w is expecting a value after -w on the command line. If you are just looking to flip a switch by setting a variable True or False, have a look at http://docs.python.org/dev/library/argparse.html#action (specifically store_true and store_false)
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('-w', action='store_true')
where action='store_true' implies default=False.
Conversely, you could haveaction='store_false', which implies default=True.
Adding a quick snippet to have it ready to execute:
Source: myparser.py
import argparse
parser = argparse.ArgumentParser(description="Flip a switch by setting a flag")
parser.add_argument('-w', action='store_true')
args = parser.parse_args()
print args.w
Usage:
python myparser.py -w
>> True
Here's a quick way to do it, won't require anything besides sys.. though functionality is limited:
flag = "--flag" in sys.argv[1:]
[1:] is in case if the full file name is --flag
