View Full Version : Help with Python strings

October 20th, 2010, 01:15 AM
I don't have any experience at all in Python, so please excuse me if I'm going about this the totally wrong way, but what I need to do is find the current volume of Alsa's master channel. Here's what I have so far:

f = os.popen ("amixer -c 0 set Master 0dB+")

counter = 0

for i in f.readlines ():
counter += 1
if counter == 5:
vol_line = i

start_s = vol_line.find ("[", 0, 50)
end_s = vol_line.find ("%", 0, 50)

start_i = int (start_s)
end_i = int (end_s)
real_vol = vol_line [start_i, end_i]
print real_vol

And I get the error

File "vol.py", line 117, in main
real_vol = vol_line [start_i, end_i]
TypeError: string indices must be integers, not tuple

So I have no idea what I'm doing wrong... as far as I can see, I convert the tuple start_s and end_s into an int with the int () function, but I guess that's not happening?

If you can please help, thanks!

October 20th, 2010, 01:41 AM
The tuple is the new one you created, right there in that line that's quoted in the error message. Assuming you're going for a substring there, the correct syntax would use a colon, not a comma:

real_vol = vol_line [start_i:end_i]

Also, your int() lines are unneeded -- start_s and end_s are already ints.

October 20th, 2010, 01:46 AM
Oh, that makes way more sense. I thought it was odd find () didn't just give me an int, thanks very much!