Why does this bash call from python not work?

I am messing around with Bitcoins a bit. When I want to get some info about the local bitcoin install, I simply run bitcoin getinfo and I get something like this:

{
    "version" : 90100,
    "protocolversion" : 70002,
    "walletversion" : 60000,
    "balance" : 0.00767000,
    "blocks" : 306984,
    "timeoffset" : 0,
    "connections" : 61,
    "proxy" : "",
    "difficulty" : 13462580114.52533913,
    "testnet" : false,
    "keypoololdest" : 1394108331,
    "keypoolsize" : 101,
    "paytxfee" : 0.00000000,
    "errors" : ""
}

I now want to do this call from within Python (before anyone points it out; I know there are Python implementations for Bitcoin, I just want to learn doing it myself). So I first tried executing a simple ls command like this:

import subprocess
process = subprocess.Popen('ls', stdout=subprocess.PIPE)
output = process.communicate()[0]
print output

This works fine, printing out the list of files and folders as expected. So then I did this:

import subprocess
process = subprocess.Popen('bitcoin getinfo', stdout=subprocess.PIPE)
output = process.communicate()[0]
print output

but this gives the following error:

Traceback (most recent call last):
  File "testCommandLineCommands.py", line 2, in <module>
    process = subprocess.Popen('bitcoin getinfo', stdout=subprocess.PIPE)
  File "/usr/lib/python2.7/subprocess.py", line 710, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1327, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory

and here I'm kinda lost. Does anybody know what's wrong here? All tips are welcome!

[EDIT] Using the excellent answers below I now made the following function, which might come in handy for others as well. It takes either a string, or an iterable with separate arguments and parses the output if it is json:

def doCommandLineCommand(command):
    process = subprocess.Popen(command, stdout=subprocess.PIPE, shell=isinstance(command, str))
    output = process.communicate()[0]
    try:
        return json.loads(output)
    except ValueError:
        return output