如何使用带有条件可选参数的python argparse？

Question

Here is the current code.

import time
import collections
from modules import outputs
from modules import scrub
from modules import lookups

parser = argparse.ArgumentParser(description='AppMap Converter to Generate Asset Files from AppMapp Data')
parser.add_argument("operation", nargs='?', default="empty", help='The operation to perform')
parser.add_argument("input", nargs='?', default="empty", help='The input AppMapp File Path')
parser.add_argument("output", nargs='?', default="empty", help='The output Asset File Path')
args = parser.parse_args()

start = time.time()

if(args.operation == "Convert"):
    input_file_path = args.input
    output_file_path = args.output
    #DO LOTS OF STUFF
else:
    exit()

The script is called sacsproc, so I run it from the command line as follows:

./sacsproc Convert input.csv output.csv

This all works nicely, the problem is that I need more sacsproc commands which may have a totally different set of secondary parameters. ie one command might be:

./sacsproc Clean -rts input.csv output.csv err.csv

Thus, I am trying to determine how one defines arguments that are conditional on the first argument ? In my mind, I'm thinking about the zfs command line utilities that do what I am trying to do (eg zpool create mirror sdb sdc vs. zpool remove sda).

Answer 1

use subparsers

subparsers = parser.add_subparsers(help="sub-command help")

group1 = subparsers.add_parser("something",help="do something")
group1.set_defaults(which="g1") # some default value (so you know which group was activated)
group1.add_argument("ARG",help='do something on ARG')

group2 = subparsers.add_parser("other",help="do something else")
group2.set_defaults(which="g2") # give some default value
group2.add_argument("ARG",help='do something else on ARG')

ok ...

import argparse
parser = argparse.ArgumentParser()
subparsers = parser.add_subparsers(help="sub-command help")
g1 = subparsers.add_parser("thing1",help="bind to a port and just echo back anything it gets ... with a prompt")
g1.set_defaults(which="g1")
g1.add_argument("input",help='the input file')
g1.add_argument("output",help='the output file')
g2 = subparsers.add_parser("thing2",help="create a bridge between two ports, this is useful for generating a logfile")
g2.set_defaults(which="g2")
g2.add_argument("input",help='thie input file')
g2.add_argument("output",help='the output file')
g2.add_argument("error",help="the err file")


def print_help(args):
    print "ARGS:",args
    try:
        parser.parse_args(args)
    except:
        print "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n\n"

print_help(["-h"])
print_help(["thing1","-h"])
print_help(["thing2","-h"])