argparse store false if unspecified

python command-line-arguments argparse
siamii picture siamii · Nov 20, 2011 · Viewed 73.7k times · Source 
parser.add_argument('-auto', action='store_true')

How can I store false if -auto is unspecified? I can faintly remember that this way, it stores None if unspecified

Answer

Raymond Hettinger picture Raymond Hettinger · Nov 20, 2011

The store_true option automatically creates a default value of False.

Likewise, store_false will default to True when the command-line argument is not present.

The source for this behavior is succinct and clear: http://hg.python.org/cpython/file/2.7/Lib/argparse.py#l861

The argparse docs aren't clear on the subject, so I'll update them now: http://hg.python.org/cpython/rev/49677cc6d83a

Related questions

Python argparse command line flags without arguments

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 […

Read More
How to parse multiple nested sub-commands using python argparse?

I am implementing a command line program which has interface like this: cmd [GLOBAL_OPTIONS] {command [COMMAND_OPTS]} [{command [COMMAND_OPTS]} ...] I have gone through the argparse documentation. I can implement GLOBAL_OPTIONS as optional argument using add_argument in …

Read More
Argparse: Check if any arguments have been passed

My script should start a demo mode, when the no parameters are given. I tried this: args = parser.parse_args() if len(args) == 0: run_demo() else: # evaluate args Which gives a *** TypeError: object of type 'Namespace' has no len() as …

Read More