I am trying to call the function addPXT through argparse when type -a. Its not doing that. Read another issue, there addPXT was not in colons, tried that it says addPXT is not callable.
parser = argparse.ArgumentParser()
parser.add_argument('-a' ,action='store_const' ,const='addPXT')
results = parser.parse_args()
def addPXT():
print "hello"
python script.py -a
If you are a beginner with argparse and python, I'd recommend sticking with the default store action, which stores strings, and the boolean actions ('store_true/false'). Make sure you understand those first.
That said, here is a way of using store_const to call different functions:
In [131]: import argparse
define 2 functions:
In [132]: def act1():
...: print('act1')
...:
In [133]: def act2():
...: print('act2')
...:
In [134]: parser=argparse.ArgumentParser()
In [135]: parser.add_argument('-a',action='store_const',default=act1,const=act2);
I define both the default and the const - and specify the functions, not their names. Understanding the difference is important.
Try the default case:
In [136]: args=parser.parse_args([])
In [137]: print(args)
Namespace(a=<function act1 at 0xb07331dc>)
In [138]: args.a()
act1
Try the -a commandline case:
In [139]: args=parser.parse_args(['-a'])
In [140]: print(args)
Namespace(a=<function act2 at 0xb078c1dc>)
In [141]: args.a()
act2
If you have more arguments (dest), you could pass args to your function, if it is defined to accept them, args.a(args).
The simpler boolean argument approach:
In [146]: parser=argparse.ArgumentParser()
In [147]: parser.add_argument('-a',action='store_true');
In [148]: args=parser.parse_args([])
In [149]: print(args)
Namespace(a=False)
In [150]: if args.a:
...: act2()
...: else:
...: act1()
act1
# similarly for `['-a']`.
or if you accept strings, maybe even choices
if args.a == 'act1':
act1()
elif ...
The primary purpose of argparse is to deduce what the user wants, and issue help and error messages. Acting on that information is largely the responsibility of the rest your code.
type function is executed. See my comment on the accepted answer of your link.its accepting as a string only - elaborate. What's the error message? You need to understand the difference between function names (references) and strings. Strings aren't callable. The end of my code shows how string values could be used.argparse will call the action object during parsing but you need to supply something that looks like the Action class because the parser will use that object later. The Action doc says
You may also specify an arbitrary action by passing an Action subclass or other object that implements the same interface. The recommended way to do this is to extend Action, overriding the call method and optionally the init method.
So, create an Action subclass and have it call your function
import argparse
import sys
def addPXT():
print "hello"
class FooAction(argparse.Action):
def __call__(self, parser, namespace, values, option_string=None):
addPXT()
parser = argparse.ArgumentParser()
parser.add_argument('-a', action=FooAction)
results = parser.parse_args(sys.argv[1:])
You're missing a destoption in the add_argument to be able to reference the option.
You will then need to test if the -a option was passed as argument. If so, then call the function.
parser = argparse.ArgumentParser()
parser.add_argument('-a' ,dest="my_flag", action='store_const' ,const=True)
results = parser.parse_args()
def addPXT():
print "hello"
if results.my_flag:
addPXT()
Action object would be more appropriate.
action keyword does not support function calling in py3 docs.python.org/3/library/argparse.html#actiondest, results.a fetches the value. Or use ('-a','--my_flag',...).action keyword expects a Action-like object which should do some preprocessing on the option before the parser continues on its way. Depending on what OP wants to do, either your answer or something using an Action object is best.
argparseis for parsing command line arguments and not for calling arbitrary functions. IfaddPTXis supposed to process an argument, for later use by your program, then great. But read how the action keyword works. It has a specific role and it uses an Action object.