Execute Firefox command in Python

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.

Community · Accepted Answer · 2017-03-20 10:18:21Z

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

edited Mar 20, 2017 at 10:18

CommunityBot

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answered Feb 7, 2014 at 20:37

Stefan Arentz

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