Execute Firefox command in Python - firefox

Question

I have read everywhere that the subprocess module is the best way to use the command line from Python, but I'm having trouble making it work. I have a firefox extension called Page Saver that saves an image of an entire webpage. On the comand line, this command successfully saves an image:
firefox -savepng "http://www.google.com"
I've tried this script to automate the process, but no luck:
import subprocess
subprocess.call(['firefox', '-savepng', 'http://www.google.com'], shell=False)
I get this error:
Traceback (most recent call last):
File "C:/Users/computer_4/Desktop/Scripts/crescentsaver.py", line 2, in <module>
subprocess.call(['firefox', '-savepng', 'http://www.google.com'], shell=False)
File "C:\Python27\lib\subprocess.py", line 524, in call
return Popen(*popenargs, **kwargs).wait()
File "C:\Python27\lib\subprocess.py", line 711, in __init__
errread, errwrite)
File "C:\Python27\lib\subprocess.py", line 948, in _execute_child
startupinfo)
WindowsError: [Error 2] The system cannot find the file specified
Am I using subprocess incorrectly?
Thanks.
Update:
Found the solution. It was a little detail of the extension I was using. The script had to be run from the Firefox default saves folder to work. I also ran the parameters as a string, not a list, with shell=True:
import subprocess
subprocess.call('firefox -savepng http://www.google.com', shell=True)
I could not answer my own question due to the limitation on new users answering their own questions within eight hours of posting.

Answer 1

What subprocess.call() is telling you with that error is that it cannot find the firefox command on your PATH. (Which is a list of directories where Windows searches for commands).
So you have two options here:
Specify the full path to the Firefox command in your script: this is easy, just put the full path in your python code.
Add the directory that contains the Firefox command to your PATH. This is a little more complicated but you can find a decent tutorial on Super User