How can I run an Electrum console command from outside Electrum (in Linux)? I want to use my electrum wallet balance in my another python application.
How do I make a call to the getbalance() function?
You might find it easier to just query an electrum server directly. Stratum is a nice protocol in that it's easy to use in an ad-hoc fashion.

If you're using python3 this is almost certainly the easier solution, too.

def get_from_electrum(method, params=[]):
    params = [params] if type(params) is not list else params
    s = socket.create_connection(('ecdsa.net', 50001))
    s.send(json.dumps({"id": 0, "method": method, "params": params}).encode() + b'\n')
    return json.loads(s.recv(99999)[:-1].decode())

get_from_electrum('blockchain.address.get_balance', '1MaxKayeQg4YhFkzFz4x6NDeeNv1bwKKVA')


Result:

{
    "result": {
        "unconfirmed": 0,
        "confirmed": 237093847
    },
    "id": 0
}


Documentation: https://electrum.orain.org/wiki/Stratum_protocol_specification