Argparse, and linking to methods in Subclasses

[Victor Hooi]

Hi,

I have a simple Python script to perform operations on various types on in-house servers:

manage_servers.py <operation> <type_of_server>

Operations are things like check, build, deploy, configure, verify etc.

Types of server are just different types of inhouse servers we use.

We have a generic server class, then specific types that inherit from that:

class Server
def configure_logging(self, loggin_file):
...
def check(self):
...
def deploy(self):
...
def configure(self):
...
def __init__(self, hostname):
self.hostname = hostname
logging = self.configure_logging(LOG_FILENAME)
class SpamServer(Server):
def check(self):
...
class HamServer(Server):
def deploy(self):
...

My question is how to link that all up to argparse?

Originally, I was using argparse subparses for the operations (check, build, deploy) and another argument for the type.

subparsers = parser.add_subparsers(help='The operation that you want torun on the server.')
parser_check = subparsers.add_parser('check', help='Check that the server has been setup correctly.')
parser_build = subparsers.add_parser('build', help='Download and build a copy of the execution stack.')
parser_build.add_argument('-r', '--revision', help='SVN revision to buildfrom.')
....
parser.add_argument('type_of_server', action='store', choices=types_of_servers,
help='The type of server you wish to create.')

Normally, you'd link each subparse to a method - and then pass in the type_of_server as an argument. However, that's slightly backwards due to the classes- I need to create an instance of the appropriate Server class, then call the operation method inside of that.

Any ideas of how I could achieve the above? Perhaps a different design pattern for Servers? Or a way to use argparse in this situation?

Thanks,
Victor

 

[Karim]

with global:

SERVER = None

A the end of Argparse declarations:
parser_check.set_defaults(action=do_the_check)

parser_build.set_defaults(action=do_the_build)

Then declare the action functions:

def do_the_check(namespace_args):
if not SERVER:
SERVER = Server(namespace_arg.type_of_server)
SERVER.check()

def do_the_build(namespace_args):
if not SERVER:
SERVER = Server(namespace_arg.type_of_server)
SERVER.build()

If I correctly understood your issue.

Regards
Karim