amixer sset 'Master' 50% works on terminal but not as os.system command

Question

I'm trying to write a python program on my Raspberry Pi to mute/change the volume of the speaker output as soon as it runs. If I type:

amixer sset 'Master' 50%

on the terminal, the volume is increased by 50%.

However if I write a python file called filename.py with the following lines:

import os
os.system("amixer sset 'Master' 50%")

and run it in terminal with

sudo python filename.py

it comes up with an error

amixer: Unable to find simple control 'Master',0

How can I just run exactly the same command in terminal as I do in python?

os.system(...) takes a string as an argument. You probably meant to write os.system("amixer sset 'Master' 50%") — MadMike, Commented Feb 21, 2017 at 10:11
Sorry thats what I meant. I edited the post, thanks for pointing that out. — mnt, Commented Feb 21, 2017 at 10:16
Why do you call sudo python filename.py instead of just python filename.py? You don't seem to need sudo with amixer? — MadMike, Commented Feb 21, 2017 at 10:19
Wow! such a simple solution and its worked! Ive been trying all sorts of complicated solutions. Thanks MadMike, Im new the the forum, how can I rate this comment up? — mnt, Commented Feb 21, 2017 at 10:24
I'm going to formulate it as a answer. I may then click the check-mark on the left to accept it. — MadMike, Commented Feb 21, 2017 at 10:26

MadMike · Accepted Answer · 2017-02-21 10:34:12Z

You need to change your filename.py from

import os
os.system(amixer sset 'Master' 50%)

to

import os
os.system("amixer sset 'Master' 50%")

as os.system(...) only accepts a string as a argument.

Additional points:

Don't call sudo python filename.py if your program don't need root rights. In your case python filename.py should suffice.
It's good form to add #!/usr/bin/python to the beginning of your script. This indicates it's a python script. So your file will looks like this:
```
#!/usr/bin/python

import os
os.system("amixer sset 'Master' 50%")
```