Python argparse：如何將`--add`改爲`add`而仍然是可選參數？

Question

我想這個功能：

import argparse 
parser = argparse.ArgumentParser() 
parser.add_argument("--add", help="Add a new name to the list of names", 
        action="store") 
args = parser.parse_args() 
if args.add: 
    print "'%s' was added to the list of names." % args.add 
else: 
    print "Just executing the program baby." 

這樣：

$ python program.py --add Peter 
'Peter' was added to the list of names. 

但是，當我改變--add到add

$ python program.py add Peter 
'Peter' was added to the list of names. 

我可以--add代替add像這樣實現這一目標它不再是可選的，我怎樣才能讓它成爲可選的，但沒有那些--標誌？ （最好也使用​​庫）

Answer 1

你想要什麼，實際上被稱爲「位置參數」。 你可以這樣解析它們：

import argparse                
parser = argparse.ArgumentParser()            
parser.add_argument("cmd", help="Execute a command",       
        action="store", nargs='*')         
args = parser.parse_args()              
if args.cmd:                 
    cmd, name = args.cmd              
    print "'%s' was '%s'-ed to the list of names." % (name, cmd)    
else:                   
    print "Just executing the program baby."         

，讓你可以指定不同的操作能力：

$ python g.py add peter 
'peter' was 'add'-ed to the list of names. 

$ python g.py del peter 
'peter' was 'del'-ed to the list of names. 

$ python g.py 
Just executing the program baby. 

Answer 2

你可以使用sub-commands實現這一行爲。試着像下面

import argparse 
parser = argparse.ArgumentParser() 

subparsers = parser.add_subparsers(title='Subcommands', 
    description='valid subcommands', 
    help='additional help') 

addparser = subparsers.add_parser('add') 
addparser.add_argument('names', nargs='*') 

args = parser.parse_args() 

if args.names: 
    print "'%s' was added to the list of names." % args.names 
else: 
    print "Just executing the program baby." 

注意的是，使用nargs='*'意味着args.names現在是一個清單，不像你args.add，這樣你就可以添加以下名稱的任意數量add（你必須修改你如何處理這個論點）。以上就可以被稱爲如下：

$ python test.py add test 
'['test']' was added to the list of names. 

$ python test.py add test1 test2 
'['test1', 'test2']' was added to the list of names.