Test if an internet connection is present in python

My approach would be something like this:

import socket
REMOTE_SERVER = "one.one.one.one"
def is_connected(hostname):
  try:
    # see if we can resolve the host name -- tells us if there is
    # a DNS listening
    host = socket.gethostbyname(hostname)
    # connect to the host -- tells us if the host is actually reachable
    s = socket.create_connection((host, 80), 2)
    s.close()
    return True
  except Exception:
     pass # we ignore any errors, returning False
  return False
%timeit is_connected(REMOTE_SERVER)
> 31.9 ms ± 627 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)

This will return within less than a second if there is no connection (Linux, Python 3.8).

Note: This test can return false positives -- e.g. the DNS lookup may return a server within the local network. To be really sure you are connected to the internet, and talking to a valid host, be sure to use more sophisticated methods (e.g. SSL).

As of Python 2.6 and newer (including Python 3), a more straightforward solution which is also compatible with IPv6 would be

import socket


def is_connected():
    try:
        # connect to the host -- tells us if the host is actually
        # reachable
        socket.create_connection(("1.1.1.1", 53))
        return True
    except OSError:
        pass
    return False

It resolves the name and tries to connect to each return addres before concluding it is offline. This also includes IPv6 addresses.

Efficient way to check internet availability (modified @andrebrait's answer).

import socket

def isConnected():
    try:
        # connect to the host -- tells us if the host is actually
        # reachable
        sock = socket.create_connection(("www.google.com", 80))
        if sock is not None:
            print('Clossing socket')
            sock.close
        return True
    except OSError:
        pass
    return False